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對於今天ASML的白板講堂，我會向大家解答「EUV對系統光學意味著什麼？」
For today’s white board session, I『ll be answering the question: what does EUV mean for system optics?
在我們上一次白板講堂之後，有很多人向我們提問 「現在我們將把EUV作為我們的光源。我們需要在光學系統中做出哪些改變？」
After our last white board session we got lots of questions saying 'now we’re going to EUV as our light source. What changes did we need to make in the optics of our system?'
我們需要做的第一個重大改變是在真空條件下運行光刻機。因為眾所周知EUV光很容易被材料吸收。第二個改變是需要放棄使用透射鏡頭。如果在我們的系統中繼續使用透射鏡頭，而EUV的光進入鏡頭，就會被吸收。然而，如果使用常規的反射鏡片，它也不再會反射了，因為任何普通材料只會吸收這個波長的光。
The first big change we needed to make is we needed to operate at a vacuum. Because we all know that EUV light is absorbed quite readily by materials. The second change we needed to make is we needed to abandon the use of lenses. If we use lenses in our system and light of this wavelength that enters the lens, would just be absorbed. And we can go to mirrors, simple mirrors, but again it won’t reflect because this material would just absorb light at this wavelength.
所以我們想要使用一種被稱為布拉格反射鏡或叫作電介質塗層反射鏡的鏡片。它的基本工作原理是，將多種厚度僅為幾納米的不同類型的材料進行堆疊，通過各種組合方式，使我們可以根據特定波長的光來調整反射率。
So what we want to use is a mirror known as a Bragg mirror, or a dielectric mirror. The way it works basically is, you have stacks of different types of material. And each of these stacks is just a few nanometers in thickness and we want to find combinations of materials such that we can tune the reflectivity as a function of a specific wavelength of light.
因此，如果我們看一下材料（如矽或鉬）的反射率與光波長的關係圖，就會產生如圖的曲線（視頻中顯示）。因此，在13.5 nm的光波長處具有這種峰值反射率，這對於我們的光刻機來說堪稱完美。
So if we look at the plot of reflectivity versus the wavelength of light for materials such as silicon or maybe molybdenum, it has this type of curve. So we have this peak reflectivity at a wavelength of light at 13.5 nm, which is perfect for our scanners.
所以我們利用矽和鉬材料製作布拉格反射鏡。因此，對於這些層中的每一層，會以一層矽，一層鉬，一層矽，這樣疊加的方式去製作。我們製作了大約40個不同的層。那麼，如果我們有入射光通過這種材料，那麼這些層中的每一層都會發出微小的反射。我們收集所有這些小小的光線反射，最終形成一個大的反射，再將光線傳輸到光刻機的其餘部分。
So we want to make a Bragg mirror out of the materials silicon and molybdenum. So for each of these layers we then create a little layer of silicon, a little layer of molybdenum, another layer of silicon and on. We make about 40 of these different layers. So what this does then if we have incident light going through this material, itty bitty reflections come off each of these layers. We then collect all these reflections and we have one big reflection that we send on to the rest of our scanner.
為此，這個表面就必須「非常「平滑。這個鏡片的尺寸直徑約為30釐米。如果把這個由蔡司公司在德國製造的鏡片，以30釐米的尺寸放大到德國國土等大的尺寸，任何表面缺陷只能是1毫米左右。所以這鏡片是非常平滑的，這可能是宇宙中最平滑的人造結構。
For this to work, this surface has to be very smooth. This size of this mirror is about 30 cm in diameter. If I would take this mirror which is manufactured by Zeiss in Germany, if I would take this 30 cm and scale it to the size of Germany, any surface defects would only be about 1 mm. so this is quite smooth this mirror, in fact, the risk of being hyperbolic. This is probably the smoothest man-made structure in the universe.So if you have any questions please post them below and thank you for watching.