Characterization Methods for Ultrathin Wafer and Die Quality: A Review

Abstract

Ultrathin silicon die is a key enabler for highperformance semiconductor devices and ultrathin packaging. The quality of ultrathin wafers and dies has a significant influence on packaging assembly yield and device reliability.The key quality characteristics of ultrathin wafers and dies are bow/warpage, total thickness variation (TTV), subsurface damage (SSD), surface roughness, and mechanical strength. Wafer and die bow/warpage cause handling and processing problems in manufacturing processes, and induce defects during various packaging assembly processes that eventually lead to device reliability issues. The wafer TTV requirement is becoming more stringent for new generations of thin and 3-D packages. SSD, surface roughness, and dicing defects have adverse effects on die mechanical strength and reliability. Therefore, characterization methods are needed for these quality characteristics to control the manufacturing processes for ultrathin wafers and dies to ensure good device performance and reliability. The following ultrathin wafer and die characterization techniques are discussed in this paper: noncontact bow/warp/TTV measurement, materialographic analysis with optical and electron microscopy, high-resolution X-ray diffraction, micro-Raman spectroscopy, scanning infrared depolarization, optical profilometry, atomic force microscopy, and uniaxial/biaxial bending tests.Index Terms-Bow, die mechanical strength, subsurface damage (SSD), surface roughness, total thickness variation (TTV), ultrathin die, ultrathin wafer, warpage.

X-ray imaging of silicon die within fully packaged semiconductor devices

“…Ideally, such a metrology would be capable of real-time measurement of the die warpage during annealing or curing processes, particularly as a means of pinpointing the impact of crucial process steps. A relatively recent survey (Marks et al, 2014) indicated that none of the currently available commercial techniques was capable of in situ and non-destructive measurement of the nature and scale of wafer or die bow/warpage across an entire die. For example, profilometry techniques, such as shadow Moiré interferometry (Post et al, 2000;Han, 2003), measure only the macroscopic warpage of the complete package, not the chip itself.…”

Nondestructive X-ray diffraction measurement of warpage in silicon dies embedded in integrated circuit packages

“…Further, packages subjected to high temperature may fail owing to flow of polymer and the associated wafer movement. A recent review (Marks et al, 2014) revealed that none of today's commercially available metrology tools is capable of measuring, in situ and non-destructively across an entire die, the nature and scale of wafer/die strain or bow/warpage. Many techniques are destructive and those that are nondestructive tend to measure the package bow which, crucially, is not the same as the wafer/die bow.…”

Investigation of Electrochemical Oxidation Behaviors and Mechanism of Single-Crystal Silicon (100) Wafer under Potentiostatic Mode

“…As shown in Figure 9b, some oxide protrusions first build up in the damaged area. Along the locations with defects, the electric field will be locally higher and the holes are gathered, thus driving the oxidation nears these damage areas and form oxide preferentially [32,35]. As p-type Si is doping with Boron, when the boron atoms accept electron, holes will be left behind as mobile major charge carries.…”