Semiconductor components are the core of the electronics assembly in automobiles. According to different manufacturers and models of automobiles, modern automobiles may require as many as 8,000 chips, and this number will only increase with the popularity of self-driving cars. Additional The electronics subsystem and the integrated circuits it uses will provide the driverless sensors, radar and artificial intelligence needed for the driverless car.
The annual production of cars and light trucks is more than 88 million, and thousands of chip products are installed in each car. The impact of the automotive industry on semiconductor manufacturing has begun to appear. A simple fact is the thousands of chips used in cars. Nothing can fail.
The reliability of automotive semiconductor parts is critical. Any chip that fails while the vehicle is in motion may result in expensive warranty repairs and product recalls, and may damage the automaker’s brand image. In extreme cases it may lead to personal injury. Injury is even life-threatening.
If an ordinary car has 5,000 chips and an automaker produces 25,000 cars per day, then even a one-millionth (ppm) chip failure rate will lead to over 125 cars a day because of the reliability of chip quality. problem.
Since semiconductors are the primary problem in automakers' fault-scheduling diagrams, first-class automotive system suppliers are now demanding that semiconductor quality can reach a one-billionth (ppb) level, and the current trend is that regardless of the number of chips, the more The more suppliers come to define the 'maximum allowed number of faults'.
The current method of detecting reliability failures relies excessively on testing and burn-in tests. As a result, the quality objectives cannot be achieved and are far apart. At the same time, auditing standards are becoming more and more challenging, and fabs have been found to be reliable at the source of chip manufacturing. Sexuality problems, because it is the lowest cost to find problems and take corrective measures at this time. To enter this growing market area, or simply to maintain market share, IC manufacturers must actively respond to this change in chip reliability requirements. .
Fortunately, for semiconductor manufacturers, the reliability of the chip is highly related to what they know: Random defects.
In fact, for well-designed processes and products, early chip reliability problems (extrinsic reliability) are dominated by random defects. Killer defects (defects that affect yield) are caused by components at time t = 0 (finally Test) Failures. Potential defects (imperfections that affect chip reliability) are defects that cause the component to fail at t>0 (after aging).
The relationship between killer defects (benefit) and potential defects (reliability) is found to affect reliability by observing the same defect type that affects yield. Both are mainly based on the size of the defects and their appearance on the component structure. Location to distinguish. Figure 1 shows examples of killers and potential defects that lead to open and short circuits.
Figure 1 The same defect type that affects the yield rate also affects reliability. It is mainly based on the size of the defects and their position on the pattern structure.
The relationship between yield and reliability defects is not limited to specific defect types; any type of defect that may cause loss of yield may also cause reliability problems. Failure analysis shows that most reliability defects are actually process-related. The defects are traceable to the fab. Because yield and reliability defects have the same root cause, improving yield (by reducing yield-related defects) will increase reliability.
The A curve in Figure 2 shows the typical yield curve. If we only consider the chip yield, then at some point further investment in this process may not be cost-effective, so the yield rate tends to increase over time. For smoothness, the dotted line B in Figure 2 shows the curve of the same factory that manufactures the same product. However, if they want to supply the automotive industry, they must also consider the cost of insufficient reliability. In this case, Further investment is needed to further reduce the defect density, which can both increase the yield and enhance the reliability required by automotive suppliers.
Figure 2 Yield curves for different types of fabs (yield vs. time). The A-curve is applicable to fabs in the non-automotive industry. The main concern is the fab's profitability. At some point, the yield has been High enough, it is not practical to continue to try to reduce the defect rate. The dotted line B also includes the yield curve of reliability. For integrated circuit products used in the automotive supply chain, additional investments must be made to ensure high reliability, which is related to benefits. closely related.
The transition from a generic chip supplier to an automotive supplier requires a paradigm shift in fab management. Successful semiconductor manufacturers in the automotive industry have already adopted the following strategy: The best way to reduce potential (reliability) defects is to reduce wafers The overall random defect level of the plant. This means that there is a world-class strategy to reduce defects, including: improving baseline yields, reducing the incidence of anomalies, detecting them quickly when they are anomalous and repairing them online, and using crystal screening to eliminate suspicious The grains.
