Quantitative measurement of local elasticity of SiO_x film by atomic force acoustic microscopy

In this paper the elastic properties of SiOx film are investigated quantitatively for local fixed point and qualitatively for overall area by atomic force acoustic microscopy （AFAM） in which the sample is vibrated at the ultrasonic frequency while the sample surface is touched and scanned with the tip contacting the sample respectively for fixed point and continuous measurements. The SiOx films on the silicon wafers are prepared by the plasma enhanced chemical vapour deposition （PECVD）, The local contact stiffness of the tip-SiOx film is calculated from the contact resonance spectrum measured with the atomic force acoustic microscopy. Using the reference approach, indentation modulus of SiOx film for fixed point is obtained. The images of cantilever amplitude are also visualized and analysed when the SiOx surface is excited at a fixed frequency. The results show that the acoustic amplitude images can reflect the elastic properties of the sample.

IC Surface Corrosion Inspection by C-Mode Scanning Acoustic Microscopy

C-mode scanning acoustical microscopy, C-SAM, is widely used in plastic package evaluations and for failure analysis. It permits to detect subsurface delaminations, cracks and pores （air bubbles） for different microelectronics packages. In this study, abnormality was observed in C-SAM daily test, the images showed no delaminations but inhomogeneities on the IC surface. Corrosion was found by optical microscope and scanning electron microscope after decapsulation. It can be revealed as the acoustic impedance is different between corrosion and normal area. The presence of inhomogeneities and discontinuities along ultrasonic waves＇ propagation paths inside the matter causes modifications in the amplitude and polarity of ultrasonic waves. However, C-SAM＇s capability in detecting IC surface corrosion has not been presented. The capability will be illustrated and the inspection mechanism will be discussed in this paper.

Non-invasive and low-artifact in vivo brain imaging by using a scanning acoustic-photoacoustic dual mode microscopy

Photoacoustic imaging is a potential candidate for in vivo brain imaging,whereas,its imaging performance could be degraded by inhomogeneous multi-layered media,consisted of scalp and skull.In this work,we propose a low-artifact photoacoustic microscopy(LAPAM)scheme,which combines conventional acoustic-resolution photoacoustic microscopy with scanning acoustic microscopy to suppress the reflection artifacts induced by multi-layers.Based on similar propagation characteristics of photoacoustic signals and ultrasonic echoes,the ultrasonic echoes can be employed as the filters to suppress the reflection artifacts to obtain low-artifact photoacoustic images.Phantom experiment is used to validate the effectiveness of this method.Furthermore,LAPAM is applied for in-vivo imaging mouse brain without removing the scalp and the skull.Experimental results show that the proposed method successfully achieves the low-artifact brain image,which demonstrates the practical applicability of LAPAM.This work might improve the photoacoustic imaging quality in many biomedical applications which involve tissues with complex acoustic properties,such as brain imaging through scalp and skull.

Scanning Electron Acoustic Microscopy of GaInAsSb by Metalorganic Chemical Vapor Deposition

Scanning electron acoustic microscopy (SEAM) is a new technique for imasing and characterization ofthermal, elastic and pyroelectric property variations on a microscale resolution. The signal generation mechanisms and the application of scanning electron acoustic microscopy in GalnAsSb alloy grown by MOCVD wereinvestigated. Defects below the surface of GalnAsSb alloy were found by SEAM images and cathodelumi-nescence. The results show that electronacoustic imaging has its own features over secondary electron imag-ing.

Ferroic domain characterization of Ni_(55)Mn_(20.6)Ga_(24.4) ferromagnetic shape memory alloy

The microstructure and coupling between structural and magnetic domains of ferromagnetic shape memory alloy Ni55Mn20.6Ga24.4 were investigated by scanning electron acoustic microscopy （SEAM）. Stripe ferroelastic domains （martensite variants） exist in every grain, and exhibit the configurations of the typical self-accommodation arrangement. Magnetic domain structure of Ni55Mn20.6Ga24.4 was observed by the Bitter method and magnetic force microscopy （MFM）. Due to the unique subsurface imaging capability of SEAM, combined with the Bitter method, the ferroelastic domain structure can be compared with in situ ferromagnetic domain structure. It is found that the martensitic variant boundaries coincide well with the ferromagnetic domain walls, which is beneficial for the understanding of the correlation between two kinds of ferroic domains.

Detection and formation mechanism of micro-defects in ultrafine pitch Cu-Cu direct bonding

In this paper, Cu-Cu interconnects with ultrafine pad pitches of 6 p.m, 8 p.m, and 15 p.m are implemented on the 12 inch wafers by a direct bonding process. Defects are not found by traditional non-destructive （NDT） c-mode scanning acoustic microscopy （c-SAM）. However, cross sectional observation of bonding interfaces reveals that micro-defects such as micro seams are located at SiO2 bonding interfaces. In order to examine the micro-defects in the ultra-fine pitch direct bonding process by the NDT technology, a novel ＂defect-enlarged approach＂ is proposed. The bonded dies are first annealed in an N2 oven at 300 ℃ for a few hours and then cooled quickly in air. The c-SAM scanning images show large defects at the place where nothing can be detected by c-SAM before this treatment. Cross sectional observation of the bonding interfaces indicates that these defects consist of large size micro seams at the SiO2 bonding interface, especially near Cu pads with an ultrafine pitch of 6μm. However, these large defects disappear after several hours at room temperature, observed by c-SAM. It is inferred that the disappearance of these defects inspected by the ＂defect-enlarged approach＂ results from the combination of intrinsic micro seams and ＂weak＂ bonds in the silicon oxide layer. Then the underlying physical mechanism of these micro-defects is proposed, which is influenced by Cu pad surface topology and bonding models.

Combining infrared and mode synthesizing atomic force microscopy： Application to the study of lipid vesicles inside Streptomyces bacteria

We propose a new analytical approach combining vibrational spectroscopy and acoustic tomography for the detection and characterization of vesicles inside Streptomyces bacteria. Using atomic force microscopy and infrared spectroscopy （AFM-IR）, we detect the presence of triglyceride vesicles. Their sizes in depth are measured with high accuracy using mode synthesizing atomic force microscopy （MS-AFM）. We conducted a comparative study of AFM-IR and MS-AFM, and highlighted the advantages of the coupling of these techniques in having a full characterization （chemical, topographical, and volumetric） of a biological sample. With these complementary techniques, a complete access to the vesicle size distribution has been achieved with an accuracy of less than 50 nm. A 3D reconstruction of bacteria showing the in-depth distribution of vesicles is given to underline the great potential of the acoustic method.