ASML readies next-gen EUV pellicle for production

ASML expects to supply its customers with a new generation pellicle by the end of the year. Raising transmittance from 83 to 90 percent, it will take away some of the pain of having to use one.

Paul van Gerven

You’d think that anything reducing the amount of precious EUV radiation hitting the wafer in an EUV scanner would get the thumbs-down from semiconductor manufacturers. But they made an exception for the pellicle. Even though the membrane that keeps stray particles away from the EUV photomask will inevitably absorb some EUV radiation, thus decreasing throughput, the idea of having their costly masks open and ‘exposed’ was simply unbearable to chipmakers. ey insisted on having a way to protect it.

Since there were no takers at the time, ASML was more or less forced to take up pellicle development itself. Four years ago, its e orts reached the industrialization phase. What has happened since then? Raymond Maas, ASML’s product manager for pellicles, lls us in.

So, did your pellicle make it into fabs already?

Maas: “Indeed it did: we’ve shipped thousands of them over the past two years, to all of our EUV customers. e lms are being manufactured by Teledyne Dalsa in

Credit: ASML Canada, and then assembled and quali ed in Veldhoven. All the required tooling we had to develop in-house, because obviously it didn’t exist before.”

Originally, ASML didn’t think pellicles would be necessary because it predicted the environment inside the scanner would be clean enough. Since chipmakers are currently using pellicles, was that prediction too optimistic?

“ e inside of the scanner isn’t the only consideration. Reticles are also handled outside the scanner, during which particles can be introduced. In many cases, our customers choose to use a pellicle because they want to protect the reticle all the time, not just inside the scanner.”

“ at said, while we’ve made great strides with reducing particle density inside the scanner, I can’t say it’s perfect. It’s clean enough for some use cases; this mainly depends on the size of the chip. If the chip is relatively small, the mask pattern takes up only a small percentage of the mask’s surface, meaning the chance of a particle landing on a critical part is relatively small. is is one situation in which our customers may opt to work without a pellicle.”

How much light is absorbed by the pellicle?

“Our current polysilicon-based pellicle has a transmittance of 83 percent. EUV masks being re ective, light has to pass through it twice, so that represents a considerable loss. Of course, our customers would prefer not to use it, but it’s just not feasible to obtain the level of cleanliness in every aspect of mask handling.”

“We expect to introduce a new, metal silicide based pellicle by the end of the year, with which we target 90 percent transmittance. Equally important, however, is that this upgrade supports our roadmap, which eventually will take source power up to 400 watts. e pellicle heats up to 600 degrees Celsius at that power level, which the polysilicon couldn’t withstand.”

Now that things are up and running, and other organizations have started pellicle development, shouldn’t ASML be stepping back from this activity?

“We’ll keep driving the roadmap until there’s a pellicle with 95+ percent transmittance that ful lls all the other requirements. We feel a responsibility towards our customers to do that. However, we happily support every e ort to come up with improved designs. As we found out ourselves, though, going from lab to fab takes a lot of e ort and requires large investments.”

“Now that volumes are going up – perhaps to as much as 10,000 pellicles per year – we don’t consider ourselves to be ideally suited to keep handling the assembly. As announced last year, Mitsui Chemicals will take over in that department. We expect that Mitsui will start handling pellicle assembly by the end of this year.”

Anton van Rossum anton.van.rossum@ir-search.nl

Ask the headhunter

T.M. asks:

After having spent the last ten years abroad, I’m currently working on a one-year contract with a technology company in the west of the Netherlands in a specialist technical position. Unfortunately, my job isn’t at all as depicted when I signed on. Due to the corona crisis, an important project for which I was hired has been postponed and I don’t expect my contract to be extended. As a precaution, I’m keeping my eyes wide open.

I got this job through an English headhunter. I recently got back in touch with them when they called me for a position at another company. They told me it’s exactly the job I’m looking for, even better than what I have now. However, he would only reveal the company’s name if I agreed to an interview in advance. I went along with this on the condition that I would receive the job description and company name before the interview so that I could prepare. To my surprise, he sent a description with a profile that didn’t fit at all. I then canceled the appointment with the company because I felt misled.

Shortly afterward, I had a conversation with another agency. Earlier this year, they had introduced me to the same company, but to no avail. Following our conversation, the agency sent me a vacancy that was perfect for me, at the very same company no less! After I agreed to an exploratory meeting, I was told to be prepared for some critical questions about our previous dealings.

That’s the world upside down! Should I apologize for an agency sending me the wrong job description? Actually, I don’t feel like doing that interview at all anymore. Without having spoken to anyone, I already have to defend myself. However, I could really use a new position. What advice can you give me?

The headhunter answers:

Let me start by pointing out that it’s certainly not the fault of this company that the earlier contact went a bit messy. They’re merely looking for a new employee and using a few specialized agencies in the industry for that. They received your résumé and are interested in an introduction. That’s all.

If the planned interview is subsequently canceled, this raises questions with them. That’s only normal, I would say. You can be sure that this will be brought up in the interview, which is quite normal, too. You don’t have to apologize, but you can give a simple explanation for what happened. Stay close to the truth, is my advice. You don’t have to be ashamed of the truth because you’re looking for a new job and you want to use your own and other people’s time in a useful way. I don’t think it’s sensible to abandon a conversation altogether. You’re hurting your own cause and making yourself a victim of the situation.

It’s silly if you don’t know which company you apply to

I strongly advise you to be more critical of the agency next time and ask for a clear job description before they introduce you to the potential employer. I also think it’s silly if you don’t know which company you actually apply to. As if that’s completely irrelevant? It will look pretty strange if you have to admit that you unknowingly were introduced to the same company by two different agencies. However, if you did know, this would also raise many questions as to your social skills and integrity.