Hack IC Code through Security Fuse is a method suits for a part of microcontroller unlocking such as ATmel and Microchip MCUs, the security fuse bit normally embed in the memory;
The next step was to make the security fuse part of the memory access circuit, so that any external access to the data is disabled if the fuse is set. Usually the fuse is located very close to the main MCU memory or evhen shares some control lines with it. Also it is fabricated with the same technology as the main MCU memory array making it harder to locate and reset.
Non-invasive IC firmware hacking could still exist but would require much time and effort to find. At the same time, semi-invasive MCU crack might still work. Certainly it would take more time for engineer to find the security fuse or the part of the control circuit responsible for the security monitoring, but this could be easily automated. Performing invasive IC code attack could be more difficult as most of the work would need to be done manually, so it will certainly increase the cost and time to extract IC code.