From eegerferenc at gmail.com Fri Dec 11 22:34:38 2020 From: eegerferenc at gmail.com (=?UTF-8?B?w4lnZXIgRmVyZW5j?=) Date: Fri, 11 Dec 2020 22:34:38 +0100 Subject: [Libre-silicon-devel] OK. That happened (Funding) In-Reply-To: References: <2095836.x4sCsodQNA@lenny>

Message-ID: Hello Everyone, Regarding coherence: I digged a bit deeper into the topic. Unfortunately, it turns out that coherence and monochromaticity indeed matter. Light source in I-line and G-line steppers is usually mercury vapor discharge tube, that is polychromatic and incoherent. However, polychromaticity results in dispersion in lens material and chromatic aberration, which reduces modulation index and usable resolution significantly. Also, incoherent illumination (i.e. light source with nonzero size) results in the existence of plane wave components in pre-reticle illumination propagating with an offset angle to the optical axis. After diffraction on the reticle, higher order diffraction modes of these off-axis components would not be captured by the projection optics, resulting in incomplete image reconstruction (reduced spatial bandwidth, "blurring") at the wafer level, further reducing modulation and resolution. To counter this, illumination systems in steppers contain a narrow-band filter (Bragg-filter or similar) to filter out exactly one narrow spectral line (hence I-line and G-line), and additional optics to eliminate off-axis components and increase coherence (therefore, what reaches the reticle is more or less "laser-like", highly coherent and monochromatic radiation with very narrow FWHM). Also, the projection optics in the stepper is usually a "narrow-band" system in terms of wavelength due to dispersion, and fine-tuned to work only at the wavelength of the line it is specified for. The micro-LEDs in the JBD display, as are all other LEDs, are polychromatic (the FWHM of the one I considered in the calculation is 15nm), and it also can be assumed that coherence is not too good, too (as high coherence would mean near-zero viewing angle, which is a problem for a display). In addition, the center wavelength of the display falls half-way between I-line and G-line. In my opinion, coherence may be improved by using micro-optics at each micro-LED that produce highly collimated beams (JBD patents 10304375 and 9977152 describe microlenses and microreflectors, I don't know if they are really capable of and committed to doing this or it is just "shelling-patenting"). The wavelength of the emitters can be fine-tuned to match the nominal wavelength of the projection optics (GaAs/InGaAs LEDs are tunable to some degree by changing the Ga:In ratio). However, the effects of residual incoherence and of the 15nm polychromaticity need to be evaluated further, which is beyond my level of competence, and possibly requires the detailed knowledge of the actual projection system and/or fiddling around with one. Regards, Ferenc On Fri, Nov 20, 2020 at 12:28 PM Pavel Nikulin wrote: > On Fri, Nov 20, 2020 at 2:11 PM ludwig jaffe > wrote: > > > > - Effect of incoherent illumination on projection optics > > > > I want to note that I-line mercury lamps were incoherent, and worked > just fine before the industry switched to excimer lasers. > > I have doubts if effect on quality at such power levels, and > resolutions is a thing. > > A 1?m process should be very viable for things like smart interposers, > or other backend business. I'd say it should have an even higher > bearing on things like WLCSP because you eliminate the mask shop from > the loop every time you need to make a package modification, which can > go up to 100+ for most popular chips. > _______________________________________________ > Libresilicon-developers mailing list > Libresilicon-developers at list.libresilicon.com > https://list.libresilicon.com/mailman/listinfo/libresilicon-developers -------------- next part -------------- An HTML attachment was scrubbed... URL: From staf at fibraservi.eu Sat Dec 12 00:29:07 2020 From: staf at fibraservi.eu (Staf Verhaegen) Date: Sat, 12 Dec 2020 00:29:07 +0100 Subject: [Libre-silicon-devel] OK. That happened (Funding) In-Reply-To: References: <2095836.x4sCsodQNA@lenny>

Message-ID: <4db64594a22d5e95ae133c41246752fae12380df.camel@fibraservi.eu> ?ger Ferenc schreef op vr 11-12-2020 om 22:34 [+0100]: > To counter this, illumination systems in steppers contain a narrow- > band filter (Bragg-filter or similar) to filter out exactly one > narrow spectral line (hence I-line and G-line), and additional optics > to eliminate off-axis components and increase coherence (therefore, > what reaches the reticle is more or less "laser-like", highly > coherent and monochromatic radiation with very narrow FWHM). Also, > the projection optics in the stepper is usually a "narrow-band" > system in terms of wavelength due to dispersion, and fine-tuned to > work only at the wavelength of the line it is specified for. It is true that old steppers contain spectral line filters; more recent steppers use monochromatic lasers. But what in lithography is actually done is to use off-axis illumination for resolution enhancement. In the extreme one can reach double the resolution over coherent illumination (0.25*?/NA versus 0.5*?/NA). More info on off-axis illumination: http://www.lithoguru.com/scientist/litho_tutor/TUTOR42%20(Aug%2003).pdf Off-axis illumination can be implemented by a second lens system before the light reaches the reticle where a pupil plane is present where one can insert the shape of the off-axis illumination one wants. Actual scanners from ASML (which I am familiar with) use more complex systems with so-called diffractive optical elements to optimize for other effects like lens aberrations, light intensity uniformity, minize effect of temperature expansion of materials, etc. greets, Staf. -------------- next part -------------- An HTML attachment was scrubbed... URL: -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 488 bytes Desc: This is a digitally signed message part URL: From eegerferenc at gmail.com Wed Dec 16 16:56:46 2020 From: eegerferenc at gmail.com (=?UTF-8?Q?Ferenc_=c3=89ger?=) Date: Wed, 16 Dec 2020 16:56:46 +0100 Subject: [Libre-silicon-devel] Libresilicon status & PR Message-ID: Hello Everyone, I just went across this reddit post on Libresilicon project: https://www.reddit.com/r/chipdesign/comments/kcjfo9/thoughts_on_libresilicon_a_1000nm_foundry/ Basically, there are two major points visible here. First: it sounds if it were a necrolog for the project. Based on this, it seems our third-person public image is that we are still in an university lab in HK, not showing any progress or result in the past 1-1,5 years. Is it possible for us to counter this argument somehow, and put that on some visible place (e.g. the twitter account or on the website)? Back in 2019, the time the project moved to INL, there was a plan to make some sort of "legal entity" to interact with NLnet and INL. What is the status regarding this? Second, it seems that the final objective of the project (developing the tech node and selling ICs (Arduino clone, 555, SoC, ...) made on it, or providing the fabrication as a service, or just develop the node and leave it floating, or selling the maskless stepper as a product, or whatever) and how the project wants to reach it is not entirely clear from outside. I think this needs to be addressed and clarified. @David: Were you able to take contact to JBD? What is the status of the microscope-stepper system? Is info on it is public, or it is the private attraction of INL? Regards, Ferenc ?ger From eegerferenc at gmail.com Fri Dec 18 02:50:06 2020 From: eegerferenc at gmail.com (=?UTF-8?Q?Ferenc_=c3=89ger?=) Date: Fri, 18 Dec 2020 02:50:06 +0100 Subject: [Libre-silicon-devel] OK. That happened (Funding) In-Reply-To: <4db64594a22d5e95ae133c41246752fae12380df.camel@fibraservi.eu> References: <2095836.x4sCsodQNA@lenny>

<4db64594a22d5e95ae133c41246752fae12380df.camel@fibraservi.eu> Message-ID: <5c9e0c3d-13c3-0f7e-50d5-1a94593ef011@gmail.com> Hello Everyone, I recently elaborated further on the optical considerations of the uLED reticle topic. I put the results into the maskless litho repo as usual: https://redmine.libresilicon.com/projects/maskless-lithography/repository/43/revisions/master/entry/uLED_optics Please find errors in it... I plan to prepare a thermomechanical/thermohydraulic FEM simulation also, to study possible implementations of cooling. Regards, Ferenc ?ger On 12/12/2020 00:29, Staf Verhaegen wrote: > ?ger Ferenc schreef op vr 11-12-2020 om 22:34 [+0100]: >> To counter this, illumination systems in steppers contain a >> narrow-band filter (Bragg-filter or similar) to filter out exactly >> one narrow spectral line (hence I-line and G-line), and additional >> optics to eliminate off-axis components and increase coherence >> (therefore, what reaches the reticle is more or less "laser-like", >> highly coherent and monochromatic radiation with very narrow FWHM). >> Also, the projection optics in the stepper is usually a "narrow-band" >> system in terms of wavelength due to dispersion, and fine-tuned to >> work only at the wavelength of the line it is specified for. > > It is true that old steppers contain spectral line filters; more > recent steppers use monochromatic lasers. > But what in lithography is actually done is to use off-axis > illumination for resolution enhancement. In the extreme one can reach > double the resolution over coherent illumination (0.25*?/NA versus > 0.5*?/NA). More info on off-axis illumination: > http://www.lithoguru.com/scientist/litho_tutor/TUTOR42%20(Aug%2003).pdf > Off-axis illumination can be implemented by a second lens system > before the light reaches the reticle where a pupil plane is present > where one can insert the shape of the off-axis illumination one wants. > Actual scanners from ASML (which I am familiar with) use more complex > systems with so-called diffractive optical elements to optimize for > other effects like lens aberrations, light intensity uniformity, > minize effect of temperature expansion of materials, etc. > > greets, > Staf. > > > _______________________________________________ > Libresilicon-developers mailing list > Libresilicon-developers at list.libresilicon.com > https://list.libresilicon.com/mailman/listinfo/libresilicon-developers -------------- next part -------------- An HTML attachment was scrubbed... URL: From staf at fibraservi.eu Fri Dec 18 10:31:45 2020 From: staf at fibraservi.eu (Staf Verhaegen) Date: Fri, 18 Dec 2020 10:31:45 +0100 Subject: [Libre-silicon-devel] OK. That happened (Funding) In-Reply-To: <5c9e0c3d-13c3-0f7e-50d5-1a94593ef011@gmail.com> References: <2095836.x4sCsodQNA@lenny>

<4db64594a22d5e95ae133c41246752fae12380df.camel@fibraservi.eu> <5c9e0c3d-13c3-0f7e-50d5-1a94593ef011@gmail.com> Message-ID: <9555c2f303c0a32b9ca427fabaf0dade5814fb64.camel@fibraservi.eu> Ferenc ?ger schreef op vr 18-12-2020 om 02:50 [+0100]: > Hello Everyone, > > > > I recently elaborated further on the optical considerations of > the uLED reticle topic. I put the results into the maskless > litho > repo as usual: > > https://redmine.libresilicon.com/projects/maskless-lithography/repository/43/revisions/master/entry/uLED_optics > Please find errors in it... > > > Nice work, I agree that when using a LED matrix array it corresponds with handling each point as independent light source (this contrary to the use of micro-mirrors where off-axis would still be possible). It thus corresponds to optimization of the optics for what in lithography is called isolated features. What does stay the same is that optimization of the lens NA is a trade-off between DOF (depth-of-focus) and resolution + sensitivity to light intensity variation. The light intensity variation is caused by difference in intensity between different LEDs, the variation in intensity of a single LED over time and the non-uniform intensity over the field of the lens system. The first could in theory be corrected by varying the on-time of different LEDs although then the resolution in time has to be higher than the total 'amount' of the light in the minimum period. The focus variation is determined by the quality of your leveling system, the flatness of the top surface you want to image on and the non-uniformity of focus over the field of the lens system. In lithography this is verified experimentally by looking at so called focus-exposure (FE) matrices. This optimization can be done on a built system although money can be saved by elimating the need for high-NA from the start. The cost of lens sytem increases with increasing field size and increasing NA. greets, Staf. -------------- next part -------------- An HTML attachment was scrubbed... URL: -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 488 bytes Desc: This is a digitally signed message part URL: