Former IC failure analyst here. This sort of stuff is possible, absolutely. But it gets exponentially harder as chip geometries get smaller.
Getting through the package to the chip's top surface isn't too bad, because you can play rough with it until you get pretty close to the chip itself. So you have all sorts of fun options: wet chemistry, laser ablation, and physical milling being most common. Once you get up all in the chip's personal space, wet chemistry is probably the way to go, though nitric acid will wreak havoc on any copper elements, potentially including bond wires if they're not gold. Alternately, you can go at it with a specialized plasma tool.
Delayering the chip is time-consuming, but not prohibitively so. Your choice of wet chemistry, plasma toolsets, and physical grinding on a wheel (which works _shockingly_ well for what feels like a stone-age process). It can take a lot of practice to do this cleanly so you don't penetrate and damage a lower layer while working on an upper one, but it can be done.
The nasty bit, from the point of view of doing this outside a major megacorp, is probing and analyzing smaller geometries. As things get smaller, they get a lot more delicate. You can't just scratch through the insulative layer above metal lines with a big needle anymore, because the tip of that needle is significantly larger than multiple metal lines under it. Laser ablation can still work for mid-sized geometries, but with modern digital ICs it's all about focused ion beam tooling. That's a high-vacuum device that slowly and precisely mills and/or deposits metal with...well, an ion beam. You can get down way below the visible light range in terms of size and precision. Really cool stuff, but good luck finding one for under seven figures!
Once that's done, if your geometry is large enough to use an optical microscope, probe needles range in price from a few bucks a pop to well into the multi-hundred range. If it's too small, the next option is to get a scanning electron microscope with built-in microprobes. That's...not exactly hobbyist budget.
Doing this for an entire modern CPU-scale IC (instead of focusing on a target block) would take ages and ages and ages. I don't even want to think about it for too long. Months, at the least.
Like I said, possible...but expensive (both in engineer and tool time), hard, and time consuming. The thing is, it's time consuming because the bulk of the work of decapsulating, probing, deprocessing, and analyzing the ICs is done manually and iteratively. A TON of it could potentially be automated, but the motivation to automate all this has traditionally been pretty low because the tooling itself is so expensive that it's low-volume work.
Getting through the package to the chip's top surface isn't too bad, because you can play rough with it until you get pretty close to the chip itself. So you have all sorts of fun options: wet chemistry, laser ablation, and physical milling being most common. Once you get up all in the chip's personal space, wet chemistry is probably the way to go, though nitric acid will wreak havoc on any copper elements, potentially including bond wires if they're not gold. Alternately, you can go at it with a specialized plasma tool.
Delayering the chip is time-consuming, but not prohibitively so. Your choice of wet chemistry, plasma toolsets, and physical grinding on a wheel (which works _shockingly_ well for what feels like a stone-age process). It can take a lot of practice to do this cleanly so you don't penetrate and damage a lower layer while working on an upper one, but it can be done.
The nasty bit, from the point of view of doing this outside a major megacorp, is probing and analyzing smaller geometries. As things get smaller, they get a lot more delicate. You can't just scratch through the insulative layer above metal lines with a big needle anymore, because the tip of that needle is significantly larger than multiple metal lines under it. Laser ablation can still work for mid-sized geometries, but with modern digital ICs it's all about focused ion beam tooling. That's a high-vacuum device that slowly and precisely mills and/or deposits metal with...well, an ion beam. You can get down way below the visible light range in terms of size and precision. Really cool stuff, but good luck finding one for under seven figures!
Once that's done, if your geometry is large enough to use an optical microscope, probe needles range in price from a few bucks a pop to well into the multi-hundred range. If it's too small, the next option is to get a scanning electron microscope with built-in microprobes. That's...not exactly hobbyist budget.
Doing this for an entire modern CPU-scale IC (instead of focusing on a target block) would take ages and ages and ages. I don't even want to think about it for too long. Months, at the least.
Like I said, possible...but expensive (both in engineer and tool time), hard, and time consuming. The thing is, it's time consuming because the bulk of the work of decapsulating, probing, deprocessing, and analyzing the ICs is done manually and iteratively. A TON of it could potentially be automated, but the motivation to automate all this has traditionally been pretty low because the tooling itself is so expensive that it's low-volume work.