Analysis of main causes of failure of semiconductor components

Date：2021-09-24 17:11:01 Views：1724

In the field of consumer electronics, the quality standards of the components used are becoming more and more strict. With the wide use of semiconductor devices, their service life is degraded and eventually lead to failure. A large part of electronic components work in extreme temperature and harsh environment, resulting in failure to work normally, and a large part of components stop in laboratories and wafer factories during R & D. In addition to improper use, surge and electrostatic breakdown, which are all the reasons for the shortening of the service life of semiconductor devices, some devices running normally are also damaged and the components are degraded.

There are many reasons for the failure of semiconductor components, mainly in several aspects:

1. Design of components

Chip aging is an increasingly serious problem on advanced feature size nodes, but so far, most design teams do not need to deal with it. With the new reliability requirements put forward in automobile and other markets, these factors affecting aging need to be comprehensively analyzed, which will change greatly.

People usually know that semiconductor devices will gradually age over time, but they are unaware of the aging mechanism or the constraints leading to chip failure. In addition, according to different applications, there are certain requirements for the shortest service life of the device.

It may be 2 or 3 years for consumer equipment and 10 years for telecom equipment. Since the aging process is complex and usually difficult to fully predict, many chip designs often adopt redundant design methods to ensure sufficient margin to meet the requirements of reliable life.

"Take the operational amplifier as an example. It is the basis of many things. The operational amplifier must be biased correctly and there must be some margin in the overdrive voltage. Then you must ensure that there is enough margin, so that the aging of the operational amplifier will remain within the saturation region of the transistor over time. The overdrive margin of the transistor is shrinking because of the 7 nm power The source voltage is 750 MV and the threshold is about 350 MV, so there is almost no space to reserve a large margin. With aging, the threshold voltage can be offset by up to 50mV. If the bias circuit of the operational amplifier is offset by 50mV, it may change from the saturation region to the linear region or triode region, and the transistor will become a resistor without gain. The function of the operational amplifier is to provide gain, when the circuit becomes useless. "

Aging and reliability are challenges for simulation designers. Today's designs may not run tomorrow because they may be degraded. At present, the most important thing is to ensure that all aging and reliability requirements of the market are met.

2. Manufacturing of components

The manufacture of semiconductor devices involves measuring structures of only a few nanometers. As a reference, the diameter of human DNA strand is 2.5 nm, while the diameter of human hair is 80000 to 100000 nm. A grain of dust can destroy several bare wafers on a wafer.

If the die size becomes larger, the possibility of random failure will increase. For mature process nodes, the yield may be between 80% and 90%. However, for newer nodes, the yield may be much less than 50%, although the actual figures are strictly confidential.

"Even if the die is not catastrophic, it cannot be considered operable. If the manufacturing steps are imperfect, even the process change of one atom will produce significant differences. Although this may not affect some parts of the design, if the process change is just consistent with the critical timing path, the device may not meet the specification."

With the design gradually evolving into deep submicron technology using advanced packaging, the existing simulation tools and design methods can not well reflect the changes and their impact on reliability. This can lead to loopholes in the design process, resulting in some failures. Design processes increasingly allow changes to be considered early in development to minimize their impact, while design techniques such as redundancy can reduce the number of "almost working" chips that need to be discarded.

3. ESD protection

Generally, the chip will include ESD protection. If a voltage of 0.5V is applied to the outside of the chip, an electric field of 0.5mv/m will be generated on a medium of 1nm. This is sufficient to cause a high voltage arc. For a single die in the package, their goal is 2kJ.

"If you try to minimize ESD, or even eliminate it on these wide I / O interfaces or any type of multichip interface channel, it means that you can't really test each chip according to the same standard you have for a single chip. They must be tested more professionally because their ESD protection is very small or may not have ESD protection."

ESD events can cause problems even during operation. In portable electronic products, ESD can lead to many types of soft errors. During ESD events, noise may be caused on the power supply network (PDN) due to the sensitivity of some ICs (oscillator IC, CPU and other ICs) or the field coupling of PDN.

4. Influence of magnetic field on semiconductor

With the multifunction of smart phone and tablet computer terminals, the required power supply voltage also involves a variety of specifications. Therefore, the number of inductors used in power circuit is increasing. The integrated inductor for power circuit requires small size and supports high current, and low loss is required in some battery devices such as smart phones.

"The inductor stores energy in the magnetic field to perform its function. However, the inductor is affected not only by the electromagnetic energy generated by itself, but also by the external magnetic flux. The inductance value of the guaranteed component refers to the value in the state without external magnetic flux. Therefore, when packaging the inductor in the presence of external magnetic flux, it may not play its due role."

Therefore, EMS is a new problem that people have to worry about. The energy injection test is to inject 1W energy from 150kHz to 1GHz. At each frequency, you inject 1W of energy into the system. If you don't have enough protection, you will enter the internal circuit of the chip along the path, causing damage, or the voltage on the pin may be too high. If the voltage is too high, it will produce over-current strain.

5. Switching power supply

Now the power supply industry has come out of the market downturn in the past three or four years, but the competition in the switching power supply market is becoming increasingly fierce. China's power supply enterprises have no advantage in the world market only relying on low-cost manufacturing. At the same time, the position of foreign power semiconductor suppliers in the power supply industry has been further strengthened.

Although the market development situation is optimistic, over the past decade, Chinese switching power supply enterprises have relied on low-cost advantages to produce products that meet the quality and performance parameters requirements of world-famous OEM enterprises. In order to succeed, Chinese power supply enterprises have invested in many links, and more and more semiconductor manufacturers have adopted embedded power supply to reduce product costs, It also makes the power higher and higher.

"The higher the power, the higher the heating of electronic components. The problem caused by heating is not only that the mobile phone becomes hot in the pocket. It will lead to the degradation of transistors and their connections, which will directly affect the performance and reliability of semiconductor components."

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