I. A. Blech

Bio: I. A. Blech is an academic researcher from Bell Labs. The author has contributed to research in topics: Electromigration & Drift velocity. The author has an hindex of 7, co-authored 7 publications receiving 1860 citations. Previous affiliations of I. A. Blech include Technion – Israel Institute of Technology.

Electromigration in thin aluminum films on titanium nitride

Abstract: The aluminum electromigration drift velocity was measured at the temperature range 250–400 °C. A threshold current density was found inversely proportional to the stripe length. An activation energy of 0.65 eV was found for the drift velocity. The occurrence of the threshold is explained by opposing chemical gradients created by the atom pile‐up and depletion at the stripe ends. The threshold may explain several observations reported previously. The threshold is increased by decreasing the temperature or by enclosing the aluminum in silicon nitride. Virtually no electromigration is seen for very short aluminum stripes even at current densities above 106 A/cm2.

Stress generation by electromigration

Abstract: Stresses in aluminum thin films on TiN were studied in situ by transmission x‐ray topography. Stress gradients were seen to build up in thin aluminum films during passage of electrical currents. The stresses are more compressive in the anode regions. These stress gradients seem to be a concomitant of the backflow responsible for the reported threshold in electromigration, and can probably be correlated quantitatively with it.

Measurement of stress gradients generated by electromigration

Abstract: Stress gradients generated by electromigration in aluminum films were measured at 340 °C. The stresses were measured by combining x‐ray topography to record the effects of the film stress and scanning electron microscopy to measure the information on the topographs. At the electromigration threshold the stress gradients of 200‐μm‐long stripes are 6×1010 dyn/cm3, corresponding to an effective charge of z*=−1.2.

Thin‐film interaction in aluminum and platinum

Abstract: The interdiffusion and intermetallic formation in thin‐film sandwiches of platinum on preannealed aluminum has been investigated at temperatures in the range 200–500 °C. X‐ray diffractometer studies, sheet‐resistivity measurements, and microscopic studies were employed to follow the metallurgical reaction. It has been found that Al‐Pt interact very rapidly, leading to the formation of several intermetallics. In heat‐treated samples with thick aluminum (?6000 A), Pt2Al3, PtAl2, PtAl3, and PtAl4 were present. In others with 4000 A or less Al, platinum‐rich phases Pt5Al3 and Pt3Al2 were detected. After prolonged or high‐temperature anneals, phases comparatively richer in Al were found to grow at the expense of other phases formed earlier. The Al‐Pt interaction rate was found to be dependent on the annealing ambient, being significantly higher in forming gas, argon, or helium than in vacuum or air. Also, the intermetallic formation resulted in large stress changes in the composite Al‐Pt films due to a volume increase accompanying the formation of Al‐rich phases, which led to the loss of adhesion.

Thin Film Materials: Stress, Defect Formation and Surface Evolution

Abstract: 1. Introduction and overview 2. Film stress and substrate curvature 3. Stress in anisotropic and patterned films 4. Delamination and fracture 5. Film buckling, bulging and peeling 6. Dislocation formation in epitaxial systems 7. Dislocation interactions and strain relaxation 8. Equilibrium and stability of surfaces 9. The role of stress in mass transport.

Semiconductor device, and manufacturing method thereof

Abstract: An object is to provide a semiconductor device of which a manufacturing process is not complicated and by which cost can be suppressed, by forming a thin film transistor using an oxide semiconductor film typified by zinc oxide, and a manufacturing method thereof. For the semiconductor device, a gate electrode is formed over a substrate; a gate insulating film is formed covering the gate electrode; an oxide semiconductor film is formed over the gate insulating film; and a first conductive film and a second conductive film are formed over the oxide semiconductor film. The oxide semiconductor film has at least a crystallized region in a channel region.

Six cases of reliability study of Pb-free solder joints in electronic packaging technology

Abstract: Solder is widely used to connect chips to their packaging substrates in flip chip technology as well as in surface mount technology. At present, the electronic packaging industry is actively searching for Pb-free solders due to environmental concern of Pb-based solders. Concerning the reliability of Pb-free solders, some electronic companies are reluctant to adopt them into their high-end products. Hence, a review of the reliability behavior of Pb-free solders is timely. We use the format of “case study” to review six reliability problems of Pb-free solders in electronic packaging technology. We conducted analysis of these cases on the basis of thermodynamic driving force, time-dependent kinetic processes, and morphology and microstructure changes. We made a direct comparison to the similar problem in SnPb solder whenever it is available. Specifically, we reviewed: (1) interfacial reactions between Pb-free solder and thick metalliztion of bond-pad on the substrate-side, (2) interfacial reactions between Pb-free solder and thin-film under-bump metallization on the chip-side, (3) the growth of a layered intermetallic compound (IMC) by ripening in solid state aging of solder joints, (4) a long range interaction between chip-side and substrate-side metallizations across a solder joint, (5) electromigration in flip chip solder joints, and finally (6) Sn whisker growth on Pb-free finish on Cu leadframe. Perhaps, these cases may serve as helpful references to the understanding of other reliability behaviors of Pb-free solders.

Recent advances on electromigration in very-large-scale-integration of interconnects

Abstract: Today, the price of building a factory to produce submicron size electronic devices on 300 mm Si wafers is over billions of dollars. In processing a 300 mm Si wafer, over half of the production cost comes from fabricating the very-large-scale-integration of the interconnect metallization. The most serious and persistent reliability problem in interconnect metallization is electromigration. In the past 40 years, the microelectronic industry has used Al as the on-chip conductor. Due to miniaturization, however, a better conductor is needed in terms of resistance–capacitance delay, electromigration resistance, and cost of production. The industry has turned to Cu as the on-chip conductor, so the question of electromigration in Cu metallization must be examined. On the basis of what we have learned from the use of Al in devices, we review here what is current with respect to electromigration in Cu. In addition, the system of interconnects on an advanced device includes flip chip solder joints, which now tend ...

Electromigration in metals

Abstract: This paper provides an overview on the current understanding of electromigration in metals. The discussion is first focused on studies in bulk metals and alloys. This part includes a thermodynamic formulation of electromigration, a kinetic analysis of the atomic processes and a review of the theory. In addition, experimental results in interstitial and substitutional systems are summarised. The second part of the paper reviews the studies in metallic thin films. This emerged as an important area of electromigration studies since the late 1960s when electromigration damage was found to cause failure of conductor lines in integrated circuits. The discussion will review first the basic nature of electromigration in thin films with emphasis on the role of grain boundaries in mass transport and damage formation. Then the materials issues of electromigration will be explored according to the scaling trends in VLSI technology. Finally, the recent results of electromigration in fine lines and device contacts of dimensions in the micrometre range are discussed.