In this fifth webinar in the series, Dr. Mindaugas Lukosius (IHP) will zoom in on the experimental MPW run will be carried out by IHP, and will be based on graphene photonic modules on 200 mm Si wafers. The Si wafers will include integrated waveguide structures and well as graphene modules for the fabrication of various graphene based photonic devices. Design rules will include the basic design elements to be used in this particular e-MPW run.
Topics covered in this webinar are:
– Key features and challenges of graphene photonic integration.
– Introduction to the experimental Multi-Project-Wafer (MPW) run at IHP that will be based on graphene photonic modules on 200 mm Si wafers.
– Design rules and basic design elements to be used in this particular e-MPW run.
welcome everyone welcome to the fifth webinar in the series uh that is co-organized between euro practice and the 2D EPL on graphine so three weeks ago we had a webinar by graphia and today we have the fifth webinar in the series from ihp so today you will hear um a talk from ihp on exploring graphine photonics integration and more specifically also zooming into the experimental mpw run that is organized by ihp so before I would like to give the floor to our speaker Dr mowas Loos lucus um I would first like to uh give a short introduction to him so Dr mowas lus received his master of science in inorganic chemistry in 2006 from the University of vus in Lithuania then he continued to do PhD in chemistry his which he obtained in 2010 from the University of Oldenburg in the field of cvd depositions and development of high MIM capacitors in 2015 he joined the graphine research group and since 2018 he’s leading the 2D materials teams in the material M uh materials research department at ihp and he focuses on the development and introduction of Novel graphine modules into the BOS pilot line so so without further Ado I would like to give the word to mowas and I wish you all a very nice webinar mowas the floor is yours uh Romano thank you very much for the nice and kind introduction um so today I would like to give you the the first uh details uh how we explore graphine for the photonic integration so as Romano mentioned we are part of the 2D pilot line project and we are offering this kind of experimental mpw runs the word experimental comes here also with a meaning that is not that um qualified as you can imagine the real mpw services are running but nevertheless we make the first steps uh towards the graphine integration for the mpw services so here’s the outline of my talk I’m going to briefly introduce ihp I will briefly speak about 2D materials for the photonic applications and with the specifics of graphine for modulator uh where we think has the most uh potential and finally I will give some technical details of what you could expect if you would participate in this experimental mpw run first information about where I’m coming from so ihp is a Research Institute located in uh East part of Germany close to the border of Poland as indicated here and here some details listed I would like you to take two uh key messages from this uh slide that our main mission is to bridge the gap between the basic research and the industries and for that we are using 200 mm pilot line and we are doing state-of-the-art by SOS Technologies but also the new technologies like graphine technology is also emerging and we are doing the research on the pilot line scale to give more details about the clean room we are around 1,500 uh 1,500 square meters and we are operating uh 250 and 130 nanometer nodes for the BOS technology we are dedicating half of our time to the uh research and development activities and half of the time we are developing and uh dedicating our time uh for the mpw and prototyping services so we have five departments so we have the so-called vertical approach where we can start from the materials uh in the very early stage we can apply them in our technology line and then building the systems out of that we can provide certain Technologies as the services in um in this sense graphine is one of the research topics at ihp and here is a summary slide what we do with graphine before I go in further details so as I mentioned 200 mm is the message I want to give here standard Wafers what we are doing and we are solving these kind of um technical issues with graphine integration so we have to grow it transfer pattern passate in contact and once it’s solved we can can apply this uh methods to the fabrication of Novel graphine devices so the scope of today’s presentation and the scope of we what we are doing with graphine is the photonics we believe that graphine uh photonic devices have the potential and here is an example shown where the graphine modulator for example is put on the back end of line of our um electronic driver circuit which is also fabricated at ihp so this is basically the core of Tod pilot line uh activities what we are doing as well so we really want to make it a process development in the large scale we want to be compatible with silicon technology so everything what we do and what I am going to discuss is done in our pilot line which is SOS pilot line certainly we have to improve and we have to make sure that the devices have sufficient uh performances so this is the the the core activities with the graphine what we’re doing at ihp but let me start with a very uh BAS basic introduction of graphine so I am not going to explain all the details about graphine but um most probably many of you know that we uh graphine can be applied to different uh uh application Fields starting from flexible materials and batteries in head spreading as well as microelectronic applications at this point I would like to mention that and I would like to Define that what I’m going to speak today is a single layer of graphine as shown in this picture and it can be grown by cvd because I don’t want to have a confusion in the literature many of the works Define graphine also as an example showed in this picture yes it can be something banded it can be couple of layers and so on and so on so many of these applications do not require high quality uh graphine single layer graphine but in photonic applications and in micro electronic applications so single layer graphine is is essential and whenever I refer to graphine in in my talk I speak speaking about the single layer graphine which is grown by cvd technique so let’s start with electronic applications and the electronic applications are the most advanced one so far in graphine here I just have couple of examples uh what can be done with graphine so for example the whole sensors can be fabricated where you have four contacts of uh put it on graphine and then you can apply a magnetic field and for example you can monitor the current in in uh in the in the channel on the other hand the Gat uh configuration can also be used for the bio sensing uh applications and here is an example of the bio sensor shown which is even integrated with the micro with the simos uh circuits and this is was part of the mpw runs which was which were delivered uh earlier in the project so there were four runs which are already closed and Amo and vtt have uh delivered and produce some Gat for electronic applications and the one that is open now uh Romano also briefly mentioned that the webinar took place a couple of weeks ago and it’s still open so if you are interested in graphine for electronic sensor applications you can still apply if you’re interested and rewatch the webinar in the in on YouTube what I am interested and what we are interested is certainly the photonic application so here I I collected some of the very brief um introduction to the graphine photonics and to the material photonics application so on the left side we can see the range of materials which can be applied for the modulation for the modulator applications on the right side we are having the applications which are related to photo detection so we can see very bright uh spectral range we can see that these different materials due to the electronic structure can be applied at different wavelengths and warriors device Concepts could be made so certainly the most important one for us is graphine and I’m going to talk about this later on but this shows basically the potential of the 2D materials for the for the applications in the photonics uh area here I selected to show a couple of examples that even first products or first uh concepts are being in the market or close to the market for example Amo demonstrated some years ago all Optical all graphine Optical communication link where the graphine modelator and photod detector is used a group in Italy for example uh is working on the novel concept of the frequency mixing 2019 amberian for example launched this photod detector which is working at warriors uh wavelengths and these are just couple of examples of the products or device ideas which are realized in the photonics field certainly that there are much more of them but I’m just selecting and showing couple of them in this slide what’s most important and what’s most interesting application field is telecommunication so we all know we want to send and receive data in fast way and the amount of data which is being sent uh over the years is incre increasing dramatically this is not the latest certainly numbers but we can assume that uh the levels of the data that’s being sent is increasing uh significantly so the core element the key element of this data communication um Solutions is the so-called optical fiber or Optical link or radio link if you want to uh name it and there are two key elements in this in this Optical link on the one side we have the modulator on the other hand we have photo diet so these two um devices modulator and photod detector are the most promising in photonic ones and there are numbers of works so far more on the photod detectors than on the modulators and this shows the potential of the 2D of the graphine and 2D materials in these uh two applications let me compare uh state-ofthe-art photod detector first of all so on the left side I’m showing the germanium photod detector for example and I’m showing on the right side the graphine photod detector and you can see that the 3db bandwidth uh 3db bandwidth is basically can be defined as a frequency of the information signal when the 3db modulation amplitude is applied to the modulator to the photod detector in this case and uh we can see that the bandwidth of higher than 20065 GHz can be reached with the germanian photod detector state of germanian photod detectors very recent paper on the graphine photod detector showing the 3db bandwidth of 220 GHz so it shows uh a nice potential of graphine for the photo detection applications but there is one significant um uh difference in these two uh works and reports that whereas the photod detectors with Germania for example they integrated with bimos uh and on the other hand the graphine um photod detector integration is still in the very uh early research stages so still a lot of work has to be done and therefore in this kind of 2D uh pilot line projects we are trying to bridge this gap between the Fabrication in the lab and Fabrication in the real uh pilot line at the scope of today’s presentation is where we have the most experience doing that is the graphine modulators and I would like to give a brief introduction on the graphine uh modulators this plot illustrates the way the exitation can be done so you can see the uh energy momentum diagram of the graphine and we can see that we can excite thermally electrically optically and uh in this case the x-axis is showing us the speed how fast it can be done so we see that the thermally uh excited modulators are the slowest one therefore electrical and Optical modulators are most importance because they can be quite fast so just to illustrate the way the electrical modulators are working the way the electrical signal is then um applied so we have the signal light in our case which is Optical intensity being constant in the time and if we apply the electrical command to the optical modulator we can get uh um the optical intensity out uh controlled by the electrical command on the other hand if we use the optical um uh modulation scheme we have the same signal light but we can send another light source which we call the modulation light to the optical modulator and we can also modulate the signal light with another light source so therefore these two approaches are uh quite uh interesting and important for our particular graphine modulator applications let me explain why let me explain why graphine is good for that and let me start with this uh three uh pictures so let’s focus on the middle one so once again we are seeing the uh the RO cone of the graphine and in the um zero voltage State let’s call it like this the FMA level or the chemical potential is somewhere in between uh these two violence and conduction band so it means graphine can absorb the light as long as we shift the chemical potential up or down by applying positive or negative biases and once this energy is uh higher or lower than half of the photon length we can make the graphine transparent it means that no light is absorbing anymore in graphine and therefore we can have zero and one state if you want to call this kind of principle working in order to understand this uh phenomena we have to go a little bit deeper into the physics so we have to understand what is the complex refractive index that it has real and imaginary part and this plot is then representing how the refractive index real and imaginary parts are changing if we change the chemical potential so chemical potential as I mentioned can be changed by applying different voltages to the graphine modulator in this case so we can see that if we imagine here is a zero and one state you see that the difference is quite uh high so we see that the amplitude can be changed dramatically by changing the refractive index for the phase modulation is the same so we are modulating the real part and we see that the the changes if the F energy is shifted higher can be modulated also in a decent range so certainly this is the valid only for certain wavelength and the te mode in this case for example is simulated but this shows the potential of the graphine and explains the effect how the graphine can be absorbing or transparent in both cases very important remark here is to understand that this change between zero and one state on this in this particular case is strongly dependent on the graphine quality yeah so here is the uh literature report by showing how uh graphine quality is changing the modulation uh depth in this case we can call it or absorption rate so it depends on the on the graphine quality and this is shown by so-called scattering time in graphine so scattering time means that um the charge carriers can uh fly with without having any Collision so the higher the scattering time we have the better the performance of the refracting IND this change so this is the basic of the of this graphine um light interaction and certainly this uh effect allows us to create Warriors concept with graphine modulators so to summarize uh we have as I showed couple of slides before broad Optical response we can change the wavelength from visible to the infrared and we still have the effect graphine as I just showed had a strong interaction with the light it means we can reduce the footprint we can tune the fit level or the chemical potential by applying the gating graphine is seos compatible it’s just carbon and ideally um we can lower the power consumption in this case with this I would like to introduce you which kind of modulator what types of modulators exist yes so first one let’s start with the very simplest uh approach we have single layer of graphine and we have silicon wave guide so you can see in this illustration graphine is placed on top of the wave guide you see in this case green is a dope silicon you are making the capacitor with the dop silicon you have one contact here and one contact there so you’re building the capacitor between graphine and your adopt wave guide in this case the process is slightly complicated because you have to work with ad do silicon and you still have some losses due to the Silicon free carriers in the in the waveguide material there was a concept proposed a couple of years ago so-called dual layer graphine so instead of using one graphine layer we can put two graphine layers which are separated by the spacer which is called the space lay which is nothing else as a dialectric in between and we are then making the capacitor between first and second graphine layer or the bottom and the top graphine layer so in this case we can call it passive wave guide modulator because there is no need for the dope silicon and in this case losses or the performance of the graphine of the modulator is dependent on the graphine quality and of course contact resistance only another concept uh which attracted also our attention and where we focus the most is using the Silicon nitrate as a wave guide material so we take the same concept two graphine layers separated by the spacer layer and then we put everything on the Silicon nitroid wave cite so why silicon nitrite so it’s certainly refractive index is changed we have lower losses and we can work in the broader range of the wavelengths uh of Interest so this is the uh device which uh we have been following and in literature is also one of the most promising uh structure so I explain you a little bit of the theory why and how the graphine is good for the modulators I want to give you some of the aspects some of the insights what is important to understand if we want to do the fabrication and further the me and further do measurement so simulations are certainly playing a big role because we have not only here uh biases and voltages we also have the to deal with the um propagation of the optical modes so I just have here two examples to be shown there are much more things to be considered but here is an example of the Silicon wave guide so now it’s a cross-section you can imagine silicon wave guide and a graphine on top and in this case we having silicon nitrate just to compare the previous slide what I showed so you can see immediately that there is something different in both case so silicon for example has higher refractive index therefore the mode is being confined much more into the into the wave guide as we want to have the high interaction with graphine we want to spread uh the evanesence field out of the wave guide yes that the light graphine interaction gets higher so in this case with silicon nitrite we can do uh much more and um have the higher uh Optical mode uh in diretion with graphine so it’s only one thing you have to consider before doing your devices there are certainly types of modulators we can speak about the straight ones I will show in a couple of slides some details we can enhance let’s say the coupling by the introducing the ring structure Sy graphine then there is much more to be considered yes before you um do the full cycle of simulation fabrication and measurement so I wanted just to mention that you have to be very careful by choosing the materials waveguide design has to be adapted and people have to understand the coupling efficiency it’s very important the way the light is being coupled in the so-called grating coupler more information I’m going to show which type of applications you are interested and many many many other uh considerations what we call in the designing of your graphine photonic devices so let’s start with a couple of examples um which play a ro and um what should be considered by uh making the graphine modulator so first of all as I mentioned we need to couple the light in so this is a top view now of the modulator simplified version so you have so-called grating coupler and this is a cross-section of this gring coupler you have to couple some uh somehow the light in so you must understand the details of the uh coupling efficiency and so on you have to adjust the process flows for etching for example these two down you have to understand the pitch and and many other parameters so I want to show a small illustration here how uh the simulations could be done and basically we are shining the light um with a specific angle in 14° in this case for the specific wavelength in this case is the C band and we can see the way the light uh traveled through the wave through the gr coupler and now is propagating through the wave guide to the active area of the modulation so very important aspect is to um design your grating couplers in a way that they work in a specific wavelength and have the specific uh coupling properties if we go now to the modulator itself um here a couple of examples what uh people have been doing and what’s important in the designing the straight modulator the straight modulator is uh as I showed in the previous slide gr and coupler have a straight uh modul modulation area and then you have uh light coupling in so you have to understand and we have to focus on for example the spacer layer uh thickness yes here is shown for example if we change the spacer layer from 15 to 30 nanometers we completely change the picture of the modulation depth and um the voltages that have to be applied and further further effects on the other hand there was some reports for example that the slot wave guides are being used and the slot uh wave guides are used in order to enhance the uh the field local localization you can confine the mode between the the two wave guides in the slot form and therefore um enhance the properties of your of your light coupling and then certainly the graphine uh modulator itself the important aspect I wanted to show here with this trade modulator the modulation depth so basically the modulation depth is defined by the lowest and the highest state what I showed in the refractive index change it’s still around 0.2 DB per micrometer so one way to increase the modulation depth is to call to use so-called ring resonators and the ring resonators are certainly of interest but more details have to be taken into consideration first thing is So-Cal the critical coupling yeah so critical cing is basically defined um by the coupling loss between the the bus this is the bus uh wave guide and the resonator so they M they must match or in other words we can um understand that the critical coupling occurs when the uh when the rate at which the light is being coupled into the ring is equal to the rate at which the light is being dissipated yes due to Intrinsic losses so whenever we put graphine we are increasing the losses of the of the of the Ring resonator itself so therefore designing and understanding the critical coupling is very important so Alpha is defined by the losses in the ring itself and we can see with this a small simulation illustration how do we change the total transmission total transmission is uh T which means light in light out and how does it change uh if we are changing the alpha yes Alpha once again is the parameter which defines the losses in the ring so we can see that at at a certain point uh our transmission our T is becoming zero it means that graphine is absorbing in our case but if we still increase um our Alpha we can see that we are changing it back to the tal 1 which means that graphine is becoming transparent in this case and we can have the high modulation just by small changes I just want to illustrate it once again uh with the with the simulation picture light in light out and if we have no graphine we are in critical coupling condition uh we are basically sending the light in and it it’s being coupled into the ring but still the the total output is then defined by the bus wave C so in this case if we put graphine it’s just an illustration if we have graphine we can see that graphine is absorbing and much less light is being sent through the bus wave guide so we can actually modulate the light by adding graphine to the ring it’s also very important to understand um this critical coupling because it’s also changing another parameter which is called Extinction ratio and is defined by the minimum and maximum position of your transmission dip so if we don’t have any graphine we can design our grating we can design our ring resonator in such a way that it’s in a critical coupling condition and once we put graphine it is starting to absorb so we are reducing the extinction ratio as long as we are biasing graphine which is shown in this example as well we can go back to the critical coupling conditions because because graphine is becoming transparent in this case so you can see here the experimental result uh how applied voltage to the graphine modulator is changing basically the modulation deps or the trans Miss in other words so as I showed you in two slides before with the straight modulators we are at around 0.2 DB is just a number to for the reference and in this case we can increase significantly the modulation depth certainly there are further more uh parameters which have to be discussed but just to illustrate the importance of the Ring resonators is uh demonstrated with these couple of illustrations so these are the fabricated devices how they look in reality um basically the straight ones is just a wave guide with the active graphine area in the ring case um is the ring is demonstrated here and with the maender modulations modulators which which I did not uh present in detail uh uh also fabricated and given as an example in this picture so to summarize the modulator part um this is the stateof art result of the graphine modulator um which has rather High complexity of integration so you can see here that each graphine layer so the top and graphine bottom graphine layers they are Incorporated with exagonal Boron nitrite which is needed let’s say to shield graphine from from the environment um the offers also put half oxide as a high K uh material in as a spacer layer in order to increase the capacitance and they reached the 3db bandwidth of around 40 GHz so this is so far to my knowledge is the record Val which was demonstrated and this plot basically summarize the summarizes the potential and um uh application as graphine for the modulator for the highspeed operation so on this axis we see if we increase the mobility we directly increase bandwidth certainly there is also the RC component involved and we have to optimize the contact resistivity and if we see if we reduce the contact resistivity from one .7 kiloohms to 500 ohms micrometer so the and we have decent mobility of graphine we can really reach very high speeds of the modulation of 3db bandwidth and we can be very very compati uh uh competitive with the state-of-the-art Silicon uh modulators okay so this was the introduction uh of the graphine modulators and uh graphine for photonic applications I hope I showed you a couple of details why graphine is good for that and what state ofth art in the second part of my talk I would like to focus a little bit on the experimental mpw run which we are going to um provide and offer so this is the basic building block don’t understand it that this is the final device I just want uh that um people understand uh the basic idea of the concept of this uh mpw run so we have to standard silicon substrate we have the bottom cladding layer and we have silicon nitrite as a wave guide material we put one layer or two layers of graphine and then we can realize contact to this both graphine layers which is then covered by the top top cladding uh top cladding um silicon oxide so here are more specific already device architectures that we could think of certainly it does not mean that we can uh do them in one run and that if it’s possible at all to do uh many of these um uh Concepts but let me group a little bit them if we speak about the optical let’s say uh modulation um with other light source so you don’t need the contacts you can have so-called the passive uh graphine modulators where wave guide is formed and you have a graphine layer on top and then covered with the passivation layer and the top glading it will also have an option to have the metal heaters if you want to induce any heating effects to your devices in this middle uh picture we uh demonstrate that graphine uh can be put on the wave guide and if there is if there are device Concepts that require contacting one graphine layer we could do uh graphine contacting from the top the most advanced one and the most complicated at the same time is so-called this dual layer graphine what I just showed in a couple of slides previously will be done with the bottom contacting and then I will will show in the next slid a little bit more details about the so two graphine layers separated by the spacer and the contacts are done from the bottom I would like to give some details about the flow uh it’s listed uh the step by step here and I will try to show the illustrations uh certainly the the fabrication steps so I mentioned we are starting with the standard silicon Wafers and we are putting the we can put the bottom cladding of silicon oxide in the range of 500 nanom to 3 micromet so if your design requires 1.2 or 1.6 microm it’s realizable the Silicon nitrate wave guide material which I mentioned is maximum limited to 500 our most experienced and most advanced uh uh state is 400 nanometers uh you could keep it in mind if you are interested in uh um the experiences and the um properties that we have already already so in the next step we have to apply a liography step and we have to form grating couplers and the wave guides itself what I mentioned small uh illustration of the grating coupler that can be done if you use as I mentioned in our case 400 nanometers and if you edge half of that in and your period is around 1 micrometer you could expect a losses per grating coupler of around 60 BS so this is our experience what we have but certainly different design of grating couplers uh can be realized then we are putting on top of this wave guide material another silicon oxide layer and we do so-called chemical mechanical polishing where graphine where silicon nitride is then embedded and has a flat surface uh of the Silicon oxide and silicon nitride in combination as we did that uh you see that we are using uh graphine grown on germanian process I’m not going to details in here so we are transferring the first graphine layer which is done also inhouse and just as a reference you could uh take away this uh values we have the sheet resistance of around 1.5 kilms per square and our Mobility is around 1,000 after transferring the graphine so first graphine is done we are patterning it in the dimensions and the shapes um you would like and then we are putting the spacer layer and do the same uh step with the second graphine layer which is followed by another perservation layer we of course have to cover everything with the top clading layer and the top glading layer is again uh we could uh realize some structures within the range of 500 to 3 micrometers of silicon oxide as for the contact as I mentioned we have different uh um approaches depending on the designs and on the needs uh if we do the bottom contacting approach we are around 2.1 kiloohm uh uh micrometer and if we are using the top contact approach for single layer graphine we could go as low as 300 ohms micrometer so these are just uh uh key values to take away in case um any designs are being um done in the very last few slides I would like to show the details of the pdk pdk stands for the process design kit and as I mentioned in the very first slide that ihp we are offering uh more advanced and more qualified Technologies and they all have the pdk and so on and so on so we try to do with graphine uh the very basic First Steps uh in order to help the designers to fully understand our process capabilities so we have layer table we have DRC check and we have the first uh uh uh pells and scripts for the filler generation for example so let let me give you a very few details I don’t want to bother you with the many of the technical stuff so in case of interest um we will provide the initial document with the layout rules each layer that will be used in this experimental run is listed and will be provided to you so you have to use the the layer table as in the standard uh Technologies what you might know and the design rules are also given with the minimum spacings and so on and so on what you would have to do is to draw the the seal ring uh meaning that you have to frame um and put all of your designs in inside this Frame and this is available in in teda as a P cell and we are working uh now to provide this um ihp graphine pdk in K layout as soon as possible so once you draw this uh seal ring you are free to draw your structures two things you have to consider is to um that the wave guide fabrication and the metals fabrication requires the fillers here is the example of the metal so you see this box is just our metal uh material and then you have to generate the fillers around you see everywhere is NI nicely generated except the area that we have to avoid the same is applied for the wave guides and we see that this is the wave guide now box drawn and if we generate the fillers everywhere else is generated except area that is uh not needed to be uh processed I will certainly provide more details in case of interest but this just the basic information um what we are offering or what we so far have developed for this experimental run DRC check is certainly very important aspect because uh we want to get and receive the GDs files which are clean so here’s an example of shown of violated DRC check you see the contact uh pad you see the active area and you see that the contacts are drawn in the wrong place and you are violating the minimum rule for example of the of the distance to the edge and the DRC check uh will basically give you this information that you have uh time to correct uh these issues once again it’s already available in ITA and then will be available soon in a k layout okay so with this I’m coming to the my last slide uh with some details if you are interested feel free to contact us um there is also in the 2D PL or graphine Flagship website uh the link uh you can uh directly write to us and we hope that Euro practice um um access will also be organized um um soon and the dates to remember is the 14 of October so you have time until the 14th of October which is the hard deadline I encourage if any of the interest to contact us as soon as possible to discuss all the details you have to sign an NDA and we certainly have to uh understand your needs and we have to see if we can uh realize your exact uh designs okay with this I would like to thank uh the audience and here my contact details feel free to contact me at any time
1 Comment
interesting, thanks