Correct. UNM's patent claims the use of two resist coatings (which is part of some DP schemes) but with interferometric exposures (which is definitely not part of DP). Two exposures and two etches is becoming quite common, but is not new. Pitch reduction DP (the objective of US6042998) is practiced with single exposure and Dep/Etch, not infringing on US6042998.
Prior art search is actually quite difficult to be thorough and requires time-consuming practice to become more efficient. Since the inventor in general is pretty familiar with this technology, he/she can find the stuff pretty quick and then pass it along to the lawyers for discussion of what to do. But I am more surprised by how come the USPTO didn't screen inventions better. I can only guess they are not as well trained in the relevant arts.
After some more digging, I found US5424154 was already years ahead of this UNM patent, while essentially doing the same thing.
If two companies develop the same idea in secrecy at a similar time, I would have thought that made the idea obvious to someone trained in the art. Also this one sounds like something they never did in the past (pre 32nm) because it wasn't necessary to think about it. The idea of using interference patterns to deduce detail is almost as old as laser interferometry. It's used in the X-ray spectrum as well (in reverse) for imaging atomic sized particles. It's a bit like making drawing current from a battery a different patent than charging a battery.
The more I see what's happening in the patent world the more I think they should scrap patents altogether and have science advance at the rate it did before patent trolls. It's either that or put some real tests in place for patents.
1. Not obvious to someone in the field.
2. Not a direct replication of nature.
3. Not a logical extension of something existing.
4. Must be a device, not a business process or piece of SW.
Item 1 is already part of patent legislation, but no one seems to care??
US6042998 applies to a combination of at least two photoresist-defined patterns in different photoresist layers coated at different times. I don't think that is currently practiced as currently targeted double patterning, but you never know in the future. That said, UNM is showing bad form almost as a patent troll, and has no case against prior art, e.g., US5827761. Companies licensing from such as UNM must be too busy to check prior art. Engineers must learn to do this, can't just rely on lawyers.
@Kiran_NSN--I don't know the definitive answer to your question. But I would think UNM would have had to have tried to discuss this with Intel prior to filing a lawsuit. It seems like filing the suit as the opening move would be the wrong way to approach it, in my opinion. Obviously they didn't get the response they wanted from Intel, and perhaps they had trouble even getting Intel's attention or cooperation.