Ultrathin Wafer Pre-Assembly and Assembly Process Technologies: A Review

Abstract

Ultrathin silicon wafer technology is reviewed in terms of the semiconductor applications, critical challenges, and wafer pre-assembly and assembly process technologies and their underlying mechanisms. Mechanical backgrinding has been the standard process for wafer thinning in the semiconductor industry owing to its low cost and productivity. As the thickness requirement of wafers is reduced to below 100 mm, many challenges are being faced due to wafer/die bow, mechanical strength, wafer handling, total thickness variation (TTV), dicing, and packaging assembly. Various ultrathin wafer processing and assembly technologies have been developed to address these challenges. These include wafer carrier systems to handle ultrathin wafers; backgrinding subsurface damage and surface roughness reduction, and post-grinding treatment to increase wafer/die strength; improved wafer carrier flatness and backgrinding auto-TTV control to improve TTV; wafer dicing technologies to reduce die sidewall damage to increase die strength; and assembly methods for die pick-up, die transfer, die attachment, and wire bonding. Where applicable, current process issues and limitations, and future work needed are highlighted.

Polycyclic Aromatic Hydrocarbons as Sublimable Adhesives

“…Previous research on wafer thinning has focused on two aspects: (i) improving existing equipment and techniques for processing, 12,13,18,19 and (ii) studying the mechanics of crack propagation to avoid fracturing. 18−21 While these efforts have led to improvements, the typical method for processing silicon wafers has remained relatively constant for the past six decades.…”

Contactless pick-and-place of millimetric objects using inverted near-field acoustic levitation

“…Handling small components is crucial in microelectronics 1 and in the assembly of microelectromechanical systems (MEMS). 2 Gravity and inertial forces play a major role in the manipulation of large objects; in contrast, the manipulation of small components is dominated by surface forces (e.g., electrostatic and van Der Waals).…”

Curved OLED microdisplays

“…The main advantage here is that compared with pure oxide layers, the flexibility of HCs is greatly improved. The mechanical resistance of HCs is sufficient for the intended application proposed in this work: OLED circuits covered with HC materials can be easily diced using a standard saw dicing process, 20 can be handled and manually cleaned using soft cloth and alcoholic solvents in order to have a clean surface for further integration into a microdisplay housing optical system. HC1 and HC2 are based on same precursors, but the difference of synthesis and formulations made them significantly different in terms of structure and morphology.…”