Scanning Acoustic Microscopy

New applications in the field of micro systems technology require a hermetically sealed package with a high mechanical strength in order to ensure functionality of these systems. Bonding defects like voids, air inclusions and impurities in the interface can cause a local degradation of the bond. Due to the formation of cracks, the functionality may deteriorate as well, causing premature failure of the device. The Scanning Acoustic Microscopy (SAM) is a nondestructive method for the detection of these microscopic and macroscopic defects. It enables the characterization of the bond interface during manufacturing process at chip and wafer level and thereby increases the yield. An additional field of application is the analysis of single chips in order to detect defects directly related to cyclic, thermomechanical loading of the MEMS devices for a noninvasive reliability analysis.

Advantages of the test method:

• Nondestructive Analysis of chips and wafers with multi layers
• Characterization of systems with metallic interlayers
• Detection of defects in housed MEMS (even after Thermal cycling)
• Surface analysis using ultrasonic special transducers
  

The Fraunhofer ENAS offers analysis, utilizing an ultrasonic scanning acoustic microscope SAM 300 E of PVA TePla Analytical Systems GmbH. The measurements can be carried out for chips as well as wafers with a 4”, 6”, 8” and 12” diameter.

Examples of ultrasonic transduces:

transducer	depth of penetration	resolution	field of application
110 MHz	large	medium	detection of defects, voids, impurities, cracks in the bond interface of MEMS devices
175 MHz	medium	high
20 MHz	large	small
100 MHz	surface	medium	surface characterization
400 MHz	surface	High
specification
maximum substrate size		320 x 320 mm²
wafer carrier		4", 6", 8" and 12"