Failure Analysis of Semiconductors

Generally speaking, it is difficult to avoid minor failures in the development, production, and use of semiconductor devices. With the increasing demand for product quality, failure analysis has become more and more important. Through the analysis of specific failed chips, circuit designers can find problems caused by device design defects, process parameter mismatch, unreasonable peripheral circuit design, or operator error. The necessity of failure analysis for semiconductor devices is mainly reflected in the following aspects:

(1) Failure analysis is a necessary means to determine the failure mechanism of device chips;

(2) Failure analysis provides necessary basis and information for effective fault diagnosis;

(3) Failure analysis provides necessary feedback information for design engineers to continuously improve or repair chip designs to make them more reasonable and compliant with design specifications;

(4) Failure analysis can provide necessary supplements for production testing and necessary information basis for verifying and optimizing the testing process.

For the failure analysis of semiconductor diodes, transistors, or integrated circuits, electrical parameter testing must be performed first. After visual inspection under an optical microscope, the outer package should be removed, while maintaining the integrity of the chip's function and trying to keep the internal and external leads, bonding points, and chip surface undamaged for the next analysis.

Scanning electron microscopes and energy spectrum analyzers are used for this type of analysis, including micro-morphological observation, finding the failure point, observing and locating the defect point, accurately measuring the micro-geometry size of the device, and rough surface potential distribution and logical judgment of digital gate circuits (using voltage-contrast imaging methods). Energy spectrum analyzers or spectrum analyzers are used for this type of analysis, including microscopic analysis of elemental composition, material structure, or contaminants.

1. Surface Defects and Burnout of Semiconductor Devices

Both surface defects and burning of semiconductor devices are relatively common failure cases. As shown in Figure 1, it is a defect in the purification layer of an integrated circuit.

Figure 2 shows surface defects in the metallization layer of an integrated circuit.

Figure 3 shows the breakdown channel between two metal strips of an integrated circuit.

Figure 4 shows that the metal strip on the air bridge in the microwave device collapses and deforms skewedly.

Figure 5 shows the grid burnout of a microwave tube.

Figure 6 shows the mechanical damage of the metalization line of an integrated circuit.

Figure 7 shows the cracking and damage of the mesa diode chip

Figure 8 shows the breakdown of the protection diode at the input of the integrated circuit.

Figure 9 shows the mechanical damage to the surface of the integrated circuit chip due to impact.

Figure 10 shows the partial burnout of the integrated circuit chip.

Figure 11 shows the severe burnout and breakdown of the diode chip, with the breakdown points melted into a molten state.

Figure 12 shows the burnout of the gallium nitride microwave power tube chip, with the

2. Electrostatic Discharge (ESD)

Semiconductor devices are always under the threat of electrostatic discharge during their manufacturing, packaging, transportation, and assembly processes. The frequent movement and exposure to external static electricity during transportation can cause damage, so special attention is needed to prevent electrostatic discharge during transmission and transportation to reduce losses.

Among semiconductor devices, unipolar MOSFETs and MOS integrated circuits are particularly sensitive to electrostatic discharge, especially MOSFETs, due to their high input resistance and very small gate-source capacitance. They are easily charged by external electromagnetic fields or static electricity induction and are difficult to discharge in time, leading to the accumulation of static electricity and causing instantaneous breakdown of the device. The main form of electrostatic breakdown is the oxide breakdown, which forms pinholes in the thin oxide layer of the gate, causing a short circuit between the gate and the source or the gate and the drain.

Compared to MOSFETs, MOS integrated circuits have a slightly better resistance to electrostatic discharge, as they are equipped with protection diodes at their input ends. Once a large electrostatic or surge voltage enters, it can be conducted to the ground through the protection diodes. However, if the voltage is too high or the amplified current is too large, the protection diodes may also be damaged, as shown in Figure 8.

The several photos shown in Figure 13 illustrate the electrostatic discharge morphology of MOS integrated circuits, with small and deep breakdown points presenting a melting and splashing state. This type of electrostatic discharge results in a short circuit between the input end or the power supply end and the ground, causing device failure.

Figure 14 shows the morphology photo of a computer hard drive head that has experienced electrostatic discharge.