There is at least one company that will do it for several hundred dollars US, if you really want the ROM code. They use advanced destructive techniques, laser drills, micro-probes, liquid mercury, rare highly toxic solvents etc, to bypass or remove the protection at the wafer level. Nothing that an experimenter can do at home. Other than that you're SOL.
The way I look at it, if $500 is too much to spend to extract the ROM code, you don't really need it.
What a load of piffle! Who the hell sold you that story. Anyway its a load of misinformation.
The way its done is not to remove the protection at all. It's totally unnecessary.
The IC is depth measured by x-ray. Then the plastic encapsulation is carefully ground down by computer control to within a few microns of the top of the die in a clean air-room. The last few microns of the package are disolved by a small drop of nitic acid from a pipette and a temperature controlled oven in a couple of minutes. The die is then placed under a very high magnification ion beam electron microscope with a motor speed controlled x,y axis that is focussed on the rom part of the die. A scanning image is taken of the cell structure of the silicon and the die memory is directly read/converted from the images. There is no need to unprotect the device. With a high enough magnification you can simply look at the density variations in the silicon that represent the 1's and 0's. A photo scanner resolves the binary information from the images. It IS expensive - around $1,000 - but it's being done every day in Taiwanese silicon research sites - no big deal - if you've got the money.
BTW for those that are interested, this is a parallel process to that taken by the "government" at Langley when reading directly the magnetic structure of hard disc platters. By pointing the electron microcope at the side of the magnetic track on the platter, it is possible to recover all the data from the hard drive even though the data track on the drive has been erased many times. Providing the drive has not been erased too many times and providing there is the normal track tolerance wander variation between the magnetic heads and the rotating platters, the data can be recovered. I believe all the US drive manufacturers' ensure the head / track wander tolerance is purposely manufactured to leave this window of slack, - to make the "Government's" job easier.
Don't bother asking how I know!
Laser drills, liquid mercury, toxic chemicals? Phoooey.