How An EUV Light Source Works

hello everyone I'm Mike LaSalle with summer and there's a lot of interest with EUV lithography as an enabling technology for the semiconductor industry ciphers were all is making the UV sources and there's a lot of interest in UV lithography and UV sources so today I'll give a very brief introduction to how an e UV source works so first if we look at what UV lithography is it is a much shorter wavelength lithography so it's targeting a wavelength of about 13 point 5 nanometers compared to the 193 nanometers of today that short wavelength and the diffraction limited imaging performance provides very very good quality of imaging on the wafer itself however the short wavelengths also have a couple problems as well associated with how do you make 13.5 nanometer light which I'll talk about today as well as the fact that once we generate the e V light it bounces off a number of optics in the illuminator and the projection optics and the reticle inside the scanner such that the actual transmission of light through the scanner is quite low so the power levels we need to target are in excess of a hundred watts of power for evey light even in the introductory phase we use a technology called laser produce plasma in laser produced plasmas we take a high-energy laser illuminate a small droplet droplets about 30 microns in size it's made out of tin because tin is a fairly efficient relatively efficient generator of UV light in this wavelength generally we form a hot dense plasma by by illuminating the droplet with the high-energy laser that plasma on the order of 30 electron volts excites the tin I Tim excitation somewhere in the 4 D type electronic structure to generate the roughly 93 electron volt light which is 13.5 nanometers so as we generate that hot plasma from the droplet some of the droplet is kicked out as fragments and so we have collect those fragments off in the vessel and then we also have an emission of electrons ions and other things from the plasma as well that we mitigate inside our source to prevent that from getting to the collector which I'll talk about in a few minutes in the laser produced plasmas there are several key technologies that enable that first we have this high power what we use as a carbon dioxide infrared laser multistage laser amplifies the ink amplifies the co2 laser light it's about a 10 micron wavelength and it's about 20 kilowatts when it leaves the drive laser typically that laser is located in the sub tab at the end customer sites inside the manufacturing fabs so it's transmitted up to the actual vessel itself which is mounted against the scanner by the beam transport system which is a series of mirrors that direct the light up to the source vessel and then probably the heart of the source is where we have the small tin droplets generated by a droplet generator traversing across this vacuum vessel has to be a vacuum because almost everything absorbs evey light so we have it in a partial vacuum the tin droplets are moving across the chamber they're targeted by the co2 laser light the late hits the small droplet performs a hot plasma that hot plasma then emits the UV photons as I described in the prior page they bounce off the collector and in their focus into the intermediate focus point which is the connection point with the scanner we also if you look at what the exact layout looks like of a Siemer LPB source the co2 laser itself is actually as I says located in the sub fab it is fully interlocked inside this enclosure we have sealed beam tubes that take the co2 light which is a high-power laser of course so it's for safety they go through a the beam transport system up into the vacuum vessel where they strike the droplet and then the light goes off into the scanner inside our vessel if you want to look at it a little more carefully the the light comes through here through the back of the collector is focused down to a small point the 10 micron wavelength light is focused down to roughly 100 micron type diffraction limited size the droplets are generated here there as I said before they're about 30 microns they go across the vacuum system we have a targeting system with a series of mirrors and actuators and sensors and cameras to make sure we maintain the right targeting of the droplet which is important for maintaining conversion efficiency of converting infrared light into the e UV light as well as for maintaining dose control for the scanner which of course is very important for wafer exposures our target as I said before is about a hundred watts for the process development tools and for the high value manufacturing tools that we are starting today the target eventual target is 250 watts of power to enable more than 100 wafer per hour operation the collector Mir itself that that collects the light and reflects it into the intermediate focus is shown here as an example it's a little bit bigger than 1/2 meter in diameter highly polished because the wavelength determines the requirements on the flatness and figure of the mirror and with the short wavelength you need high precision with regards to flatness and figure the mirror itself the coating on the surface that actually reflects the e V light selectively is a multi-layer reflector made of alternating materials that selectively because of the tuning that we have with regards to the thickness these layers selectively reflect 13.5 nanometer light once that light is generated here's a here's a photo of an actual source that's getting ready to be attached to a scanner this is one of the early tools that are used for the process development just give an example of the size of the source the vessel itself is about 2 meters high it attaches up to the scanner at this small point over here and then there's a lot of the associated wiring for the targeting cameras and actuators as shown in this photo after that we will it into the cleanroom we attach it to the scanner it actually the vessel itself goes inside the scanner slow enclosure so it becomes an integral part of the overall scanner and here's an example of the drive laser located in the sub fab where the the co2 laser light comes out and then goes into up through the floor into the vessel to strike the droplet to generate a UV light and then from that generation of UV light into the scanner itself which you can see part of in this photo that's what a SML takes over to do the fine imaging needed to enable the small features that will continue the dimensional scaling and make the semiconductor Moore's law expansion continue so thank you for your time on the short introduction to how an e UV source works

Channel: Cymer

Views: 79,541

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Id: 5yTARacBxHI

Length: 6min 54sec (414 seconds)

Published: Mon Feb 05 2018