Recently, while chatting with a prominent figure in the industry, we discussed the topic of chip tape-out failures. I found this to be quite an interesting subject, so I gathered some reasons for chip tape-out failures online and would like to share them here.
1. Incorrect version of the design was used. This issue is quite critical; if the wrong ROM version is used, the chip is essentially rendered useless. This situation is not uncommon.
2. Significant bugs exist during the tape-out process. It is impossible for a chip to be completely free of bugs when it is taped out. Most bugs do not affect the main functionality and performance of the chip and can be avoided through software. However, some bugs cannot be circumvented by software, such as when the chip fails to exit low-power mode after entering it during power management. This is a major oversight; although the chip can power on, it is unusable.
3. PVT conditions were not fully considered. This corresponds to timing violations that were not cleared under different process corners before the chip tape-out. Under certain temperatures and voltages, the chip may malfunction, significantly reducing its operational range.
4. Issues with the analog interfaces of digital chips, such as latch-up problems with the pads, can lead to excessive internal transient currents, causing permanent damage to the chip.
5. Power consumption issues. If the chip meets functional requirements but has excessively high power consumption, especially for chips in the Internet of Things (IoT) domain, this can also be disastrous.
6. Security issues. Many chips are used in areas with very high security requirements, such as chips in personal mobile phones, personal computers, and servers. If there are hardware security vulnerabilities that cannot be mitigated by software, then this chip is also considered a tape-out failure.
7. Problems with internal power connections of the chip. This manifests as short circuits within the chip; if the power lines are not properly checked during chip design, this issue can also be quite fatal.
8. Poor handling of ESD (Electrostatic Discharge). If static protection is not adequately addressed, the chip may be prone to damage under certain conditions, making mass production impossible.
9. Manufacturing issues. One type occurs on new production lines, resulting in low yield and high production costs. Another type involves material problems, such as issues with a batch of wafers, leading to problems with power consumption and functionality of the produced chips. This does not count as a true tape-out failure.
10. Packaging issues. This occurs when the chip leads are not properly connected, resulting in abnormal chip functionality. Strictly speaking, this also does not count as a tape-out failure.
It is said that chip tape-out is a high-risk endeavor. How high is this risk? I conducted a small survey, and the probability is around 18%.
What causes of chip tape-out failures have you heard of or encountered? Feel free to leave a message below the public account.