Is there any research for chemical/structural method to prevent observing beneath chip packaging?
Brief answer is "no", at least at the chip level.

At board level there are a number of solutions but they all involve techniques that are probably illegal, since they amount to creating a booby trap which is at the vey least capable of destroying most of the board. And also likely corroding or setting fire to its surroundings. IIRC a military technique has been to use a thermite charge packaged with equipment.