Questions related to Microfabrication
I am having trouble sputter coating Mg on glass substrate. The adhesion is terrible during lift-off and I lose significant yield. I tested the same process with a silicon wafer, and the results were extraordinary but terrible with glass.
I know I can use an adhesion layer like titanium, but at this stage, I want pure magnesium structures.
Is there anyone with experience regarding this problem?
I am a nanopore researcher and would like to etch away the thin oxide layer that may form on SiN under ambient conditions over time. I am aware that I can use piranha solution. however, how much of the SiN will this etch? Even a few nanometers of etching will impact calculations and assumptions for experimentation. Below is the typical structure of the nanopore. Over that free-standing SiN, it is likely that an oxide layer forms. I want to get rid of it without etching away at the thickness of the SiN
Facing trouble (bonding-leakage) while using hand-pressure to pass liquid through my microfluidics device. I used UVO-cleaning instead of plasma-bonding (PB not available).
The way I cleaned the glass slide before UVO step: H2SO4 (70%) Overnight> dH2O > Soak with Methanol (~100%) > IPA (~100) > also add Acetone (~100) sometimes > UVO-treatment.
Microfluidics Channel precision = 20 um
Glass slide = Microscope cover slip 25*45mm
Please let me know if you need more clarification.
Thank you for your suggestion.
I want to manufature a chip for drop-seq. From previous studies 80-100 um depth has been used. The dripping crossing width is 94um. The drop size is required to be both 100 and 125. The inlet has some viscosity coming from cell lysate (CA-630) and Iodixanol (for cell suspension). Which depth is better and can easily realise both drop size?
I tried to find options to remove the buried oxide layer (1um) with 22-um thick patterned silicon (SOI) wafer after bonding with glass wafer.
Initially, I plan to immerse my bonded wafer to HF, but that could affect the glass wafer....
I tried to use SU-8 2150 to fabricate some micro structures (with a thickness of about 500um) with Mask Aligner. But I saw some white residue on top surface of the structure (see picture attached) after development. I used PGMEA to develop, followed by rinse with IPA. But no matter how long I developed, the white stuff was still there.
Does anyone have similar experience? What are the possible reasons for this?
I am working with SU8 2075 and I found some issues with the edge reflow.
This is the experimental protocol:
- 3'' Si wafers were used as substrates. Wafers are cleaned using ACE (10 min), IPA (10 min) Piranha (H2SO4:H2O2 3:1) (30 min), dehydration (30 min@ 250 °C).
- A quantity of SU-8 2075 was casted on the middle of the wafer. I started trying 3.6 g (that is about 1.2 g x inch, as suggeste by the manual 1 mL x inch). I tryed also to reduce the quantity to 2.5 g or 2 g of resist. I tryed to cast the resist on the middle, or span the resist over the substrate using a syringe needle or tilting the wafer.
- Wafer was moved in the spin coater and different rotation speeds were tested for the coating. First step: 500 RPM @ 100 RPM/s for 15s
Second step: desidered RPM @ 300 RPM/s for 30 s
I tryied 1000, 1500, 2000, 2500, 3000 RPM for the second step.
- The bottom side of the wafer was cleaned from photoresist excess
- Wafer was positioned over a bubble-levelled hotplate. I tryed ramp the temperature from RT to 65 °C, wait the desidered time, the ramp to 65 °C to 95 °C, wait the disedered time, with ramp rate of 5°C/min. I also tryed to put the wafer directly on hot hotplate at 65 or 95 °C.
I found the following issues:
- If the resist was casted on the middle without span it over the surface, a sort of signature of the position of the resist after the drop casting step remain after the spin coating. Probably it is related to a sort of drying of the dropped resist surface I think...
- After the spin coating step, on the edge of the wafer there is an amount of resist: the edge beads. This edge is about 2-3 mm extension on the wafer. But, when the wafer was placed over the hotplate, the edge became larger and larger and increase with the temperature and time. This is the so-called reflow process.
When I use low spin coating speed (1000 RPM), the reflow allows the edge to reach the wafer center and planarize the wafer thickness all over the substrate.
On the other hand, when I use high spin coating speed (3000 RPM), the reflow is limited and the resist thickness is due to the photoresist spin and not from the edge reflow.
At middle spin coating speed (1500 - 2500 RPM), the reflow does not allow the edge to reach the wafer center and planarize the wafer thickness all over the substrate. As consequence, I obtain large edge (about 2 cm) and small working area on the center.
I am not sure, but I would to understand if the reflow is something wanted or unwanted using SU-8. If yes, how I can have it anytimes, also with middle spin coating speed. If not, how I can avoid it?
I am trying to fabricate 150 um depth microneedles with 45% KOH solution at 90 degree. What are the best methods available to optimize and predict this procedure ? Are there any optimizations available ?
iam searching for literature similar to the book "Photolithography Basic of Microstructuring" from MicroChemicals or literature in general for lithography in microfabrication. It should explain the process steps and its meaning and influence to the results.
Maybe someone have a tip for me, I would really appreciate it.
We are having trouble sourcing a reliable supply of HSQ. Can anyone recommend a supplier in Europe?
I know the issue is probably a fundamental one with the Dow Corning supply chain & production priorities, and not with our local Ellsworth office.
I'm using SU-8 as an adhesive bonder (Kapton on silicon), but once I hardbake the SU-8 layer at 150C, the remaining solvents in the SU-8 evaporate and make bubbles, and essentially deteriorate the adhesion quality. I tried soft-bake or PEB the SU-8 at higher temperatures or hardbake with slow ramps but they weren't helpful.
Any suggestions would be appreciated,
I am interested in fabricating a particular design for a microfluidic chip used for particle sorting. Would you please kindly let me know where I can find a lab that offers a microfabrication service for a customized design in Germany, and what the expected costs are, and how much time it takes for delivery.
The premise is such that we have two independently fabricated su8 fluidic structures, we want to integrate them by bonding them together to make them functional. Any insights, standard protocols, or even brief thoughts on better ways to achieve SU-8 to SU-8 bonding by using any methods, chemical, physical, etc will be highly appreciated?.
I was wondering if anyone had advice on removing a nickel hard mask - which seems to have become resistant to my standard Nickel etch. The sample is GaN with a hard Nickel mask, which has undergone AR-Cl ICP etching. Normally I would remove the nickel using a dilute (5-10%) Nitric acid etch, however it seems like it has become resistant to this etch.
I have also tried dilute Aqua Regia, a dilute Nitric + Acetic + Sulphuric acid mix, and eventually a concentrated Aqua Regia* (* NOT A GOOD IDEA - I got excited when it changed colour and started bubbling, but on inspection it etched everything EXCEPT the residue!)
My current theory is that during the ICP etch the Nickel has reacted possibly with the chlorine to produce NiCl. I have read that this can happen around 200C - which is a little above what the ICP set temperature is at 150C - however presumably the sample can heat up above this.
I was wondering if anyone has had similar issues - and/or if there were any wet etches I could try which would etch NiCl (should this be it).
What techniques are used to make anisotropic SiO2, HfO2, and TiN thin films? (If possible)
The SiO2, HfO2, and TiN are used for the gate stack in certain MOSFETs. There are many studies were isotropic layers were created.
In the particular process that I am studying making anisotropic layers of SiO2, HfO2, and TiN , of only few nanometers each, will make the process a lot easier. However, I am not sure of its feasibility and repeatability.
Is any way or method to seal agarose pad or channels fabricated agarose gel pad to glass slides as like we do plasma bonding with PDMS to glass slides?.
I am looking to fabricate PDMS pillars which are 0.5um or 1um in diameter, and up to 10um tall. Pattern definition and etch on a silicon substrate to create the mould, using E-beam and RIE etching doesn't present too much of a problem.
When I come to mould my PDMS against this, does anyone have any advice on getting decent demoulding without too much breakage/stretching/deformation? Will this even present a problem?
I am working on a project that requires connecting the top side of a SI polished-polished wafer with its bottom side. I have been using p-type Silicon since I do anodic bonding at the end of the microfabrication and it works at a lower temp than n-type silicon. I was wondering if anybody with experience in RIE-ICP could tell me if using p-type or n-type silicon affects the etching rate and the etching quality significantly?
I am specifically looking for commercial and/or lab-made wet etchants options for etching specifically glass substrate and/or SiO2 with the underneath Si substrate. In my device, I have metal electrodes that are separated by micron gaps on top of the glass or SiO2/Si substrate. I would like to etch the underneath substrate wherever the micron gap exists and leaving the metal electrodes intact.Is there any suggestions, I appreciate your valuable suggestions in advance.
Im currently trying to simulate adhesive single lap joints with a square wave geometry on the micrometre scale. I was wondering if anyone had any suggestions on how to get the elements to fail at a reasonable stress based on my cohesive law (damage initiation was set at 2MPa), they also fail unpredictably with some failing and others remaining present for the entire simulation.
The mesh has been refined whilsts keeping the layer one element thick.
Ive looked at most of the conventional things such as ensuring element deletion is switched on etc. Im not sure if theres any other consideration needed for such a complex geometry in which the adhesive consists of both vertical and horizontal components.
Ive tried running the simulation in Abaqus Explicit and using mass scaling to try and get a usable result, however it seems to be tricky finding suitable values for time increment, mass scaling factor
The image attached represents a section of the joint near the end with the undeformed and deformed images given. (from Abaqus Standard). Any help/ suggestions would be gretaly appreciated!
I want to apply a coating to a metallic surface with micro-grates. I want the coating to be applied only on the top of the grates and not intrude into the ridges. Can anyone please tell me how can I do this with a facile and cost effective method like spraying or deep coating?
Does anyone have any experience with the wet etching of <111> Si?
I need to etch the handle layer of an SOI wafer completely.
I use a homemade Sn electrolyte to fabricate the Cu-Sn pillars with the diameter of 20-40 micrometers. But the surface morphology of Sn pillars is totally different with the Sn electrodeposit from other references. Could anyone help me with the formation mechanisms about the structures? Any evaluation is appreciated.
5" substrate clamped between two surface with orings providing a seal for the electrolyte. Does the e-field vary with localized thickness (dist from substrate to plate)?
I've created a simple cantilever MEMS structure with very thin aluminum contact pads. Through the release process of the MEMS structure, the contact pads have become damaged and therefore do not bond with wirebonds. Are there any options i have to re-deposit more metal (increase the thickness) on the metal contact pads, without affecting the rest of the structure?
i have few chips that have already been released and few chips that havent been released yet.
help is appreciated! thank you.
I'm trying to build a mask for etching metal, but I need simulation tool to get an idea of how to build one.
Is there any suitable open source software I can use to do this?
We wish to know if it is possible to create a commercial measuring product with nanoliter precision. We are creating a microfluidic device in PMMA. We wish to measure 100 ul volume of a solution with nanoliter precision. The same would have graduated markings to track the nanoliter volume change. Is it possible to create such a device with current mass fabrication tools?
We are in design phase of our project and it will help us understand if we should go ahead with it or not.
We are making microchannels by machining in Plexiglas (PMMA). We want to cover the same with Pressure sensitive adhesive tape (PSA tape) to close the channels to improve turnaround time of our prototyping stage.
The PSA tapes are usually acrylate adhesive on a backing of some other polymer. We would then conduct some surface reaction utilizing the surface chemistry of PMMA.
We are not sure that if we use PSA tape, if we could perform reaction on the tape side of the channel or not.
Please let me know if anyone has done so?
P.S. we are using microparticles, and are not sure if they would stick to the tape due to the adhesive or the chemistry.
i am currently dealing with su-8 2100 photoresist.
Hemispherical grooves expose the back of the quartz substrate to create a needle-shaped cured SU-8. and now, after developing, SU-8 is separated into two layers.
the first two layers are divided into the shape of the needle i wated, but the second layer comes from the shape of the rod that i did not wanted.
Since this is my first time dealing with SU-8 photoresist, it is not easy to solve problem.
Do you know anyone who solve this problem??
My protocol was attached below:
1. spin coating : 1000/10s, 3000rpm/ 60s
2. prebake : 65 ℃ 5min, 95℃ 20min
3. uv exposure : 4~6s
4. PEB : 65℃ 5min, 95 ℃ 10min
5. development : 10~15min(microchem developer)
I am trying to dice a 4" wafer made from Gorilla glass ( McMaster Carr 8410T3) using a Disco DAD3220 wafer dicing machine. I am having trouble getting a clean cut.
When I set the blade to cut the entire thickness of the wafer, the wafer cracks.
When I try to cut only part way throughput the wafer, the cutting is executed well but when I try to tap the wafer along the scored edge, it shatters.
Do you have any suggestions on how to work around these issues or experience with dicing Gorilla glass and could share your experiences?
Are there any important points to take into account when moving from commercially available disk electrodes (e.g., 3 mm diameter platinum disk electrodes) to a commercially available screen-printed or microfabricated electrodes?
Firstly, can anybody explain how the typical commercial disk electrodes are fabricated? Is the metal produced by an additive (sputtering) or subtractive method (or combination of both)?
I would also be interested in suggestions such as robustness (limiting number of scans, potential window, etc.), surface orientation (e.g., Au <111>), differences in surface immobilisation techniques, etc.
Thank you in advance.
If photoresist is coated over first alignment marks then how will I do 2nd alignment through MJB4 mask aligner?
I am trying to dive into the droplets microfluidic world using a low-cost microfabrication approach. However I am experiencing some issues.
Th configuration I am employing for droplet formation is a conventional flow focusing device. The oil phase is composed of hexadecane + 0'5% (v/v) Span and the aqueous phase is simply MiliQ water. However, the liquid leaks over the surface of the bottom layer. I am afraid this is because the pressure that appears in the junction is so high that the bonding that I employed to seal the device is not enough.
Apart from that, do you think that it is important to use an oil with a lower viscosity than hexadecane (as HFE) to reduce this effect?
Another point, at what extend does Aquapel help in droplet formation?
Thank you in advance for your answers
I am working with lift off technique with a negative photoresist (AZ nLOF2020) which is a cresol novolak based one.
The baking and post-exposure baking are done at 100ºC for 60s and the exposure is under 60 mJ/cm². I believe that is more than enough to avoid the excess of cross-linking. During the deposition of the film, the wafer temperature does not exceed 60ºC.
The manufacturer recommends to do the strip with DMSO (dimethylsulfoxide) or NMP (N-methyl-pyrrolidone) at 80ºC. However I am not able to completely remove the photoresist and I observe a strong adhesion between it and the wafer (SiO2 coated). Some parts are easily removed while another are strongly adhered.
- I tried: DMSO, NMP, PGMEA, and Acetone at different temperatures and times
- The film I work with is a glassy semiconductor and it is sensitive to basic media (including DMSO).
- Ultrasound bath helps to remove the photoresist but also removes the film
Does anyone experience something similar with negative photoresist? Could I try another solvent?
I'm a grad student trying to develop an alternative for syringe pumps, requesting users to share information on
- Advantages and Disadvantages of Syringe Pumps
- Bottlenecks faced in particular applications
- What are the preferred alternatives?
- How many experiments are performed annually on average?
- What is the price range you are looking at?
- Any other desirable you would want in the Syringe Pump?
Like many of you, I was coating my Si wafer molds with a silanization agent (TFOCS) using vapor deposition technique to facilitate easy removal of PDMS.
However, the last time, I unfortunately added to much of TFOCS and coated my wafers with a really thick TFOCS layer which messed up the entire geometry.
Do you have any idea how can I remove TFOCS without damaging the wafer? I have poured PDMS and remove it multiple times but it seems like TFOCS layer remains intact. I tried to clean the wafer with IPA but it did not work either.
I appreciate any suggestions,
I have horizontal Su8 beams (width 5um, height 5 um) fabricated on glass coverslips. The beams are attached to large Su8 pads around 500 um* 500 um.
A layer of Omnicoat was spun prior to Su8 deposition to facilitate release of the beams using MF26. By dipping the coverslip in MF26 for a short duration (3-5 sec) after development of Su8 I was hoping to release only the beams and have the pads still attached.
Unfortunately, I am getting either complete release (beams + pads) or the whole thing is stuck. Even after I release the beams manually using a micro-pipette attached to an XYZ positioner, within a day, the beams stick to the surface.
I have tried storing the coverslip in dry air and under water. In both cases, the beams re attach after release.
Can anyone suggest how to prevent this? It would be a great help. If any more details are required, please let me know.
I was wondering if anyone had experience with exposing SU8 from the backside of a transparent substrate and could give me an estimate for the relative exposure dose compared to a front side exposure.
The backside exposure is to prevent the overhanging profile if I exposed from the front, as positively sloped features are required.
Im trying to create 50um features which correlates to an exposure dose of 150-250mJ/cm^2. When I used the same protocol as I would for a topside exposure on silicon (produces good results) the features werent even close to being the correct height; as if they hadnt even been exposed really.
Would it be a fair estimate to try an exposure dose around 600-900mJ/cm^2, or could there be any other issue
Can I fabricate same height of main channel(h=5um) and narrow channels(5um) which is joint between two main channel(5um) through multlayer lithography?.kindly give valuable suggestions.thanks
In our microfabrication lab, we get messages to work with photoresists and e-beam resists (generally PMMA) in different work stations, because 'they can contaminate each other'. What is the reason for this, if it is indeed problematic?
I'm currently working with a microfabricated device composed by a thin PDMS sheet assembled onto a glycerol-coated glass slide. I need the PDMS to glide over the glass, hence I'm using the glycerol on the glass slide. The goal is to stretch the cells on the PDMS. However, if I want to grow cells in this device for more than 5 days in the incubator, the PDMS layer becomes stuck to the glass and I cannot stretch it. I don't know if this is due to adsorption of glycerol by PDMS or just a consequence of glycerol evaporation. Anyone has any ideas? And, in that line, anyone can suggest a compound which will also allow the PDMS to glide over the glass while not being adsorbed/evaporated? Thanks in advance!
I am trying to measure a step height of the iron. I have tried HCl with a 1:100 ratio with water, but the solution etched the alumina under the Fe as well, making my AFM data unreliable. I also tried ferric chloride, but that did not etch the iron. I believe the alumina to be alpha-alumina; it was deposited by e-beam evaporation. The alumina layer is 50 nm thick.
We are designing a MEMS pressure sensor for long-term use, hopefully years, underwater. Possibly saltwater as well. The device has metal traces and uses a typical method to measure pressure.
We need a passivation layer to protect the electronics from water and the external environment. Research papers in this topic each have very different opinions as to what layers, in what order and thickness to use. Some recommend SiNx, or SiO2, or SiON, or combinations of these layers in varying thicknesses.
Is there a good way to pick the passivation stack besides picking a few different layers and thicknesses? What are the pros/cons of using SiNx/SiO2/SiON? Can you recommend a particular stack for my application?
I'm using su-8 2025 on glass and want it to be part of my final fluidic device, but I'm having a lot of detaching problems even before entering water. How could I improve it, and what kind of promotors can I use?
We are developing a MEMS sensor that has a platinum resistance thermometer (PRT) and need to make pads for electrical contact to this device. We want to be able to make electrical contact by soldering the pads to a PCB and (alternatively) do gold wirebonding.
If we make the pads out of platinum:
Is it possible to solder to platinum pads? If so, what is a the recommended platinum thickness for soldering?
Is it possible to wirebond gold wires to platinum pads? If so, what is the recommended platinum thickness for wirebonding?
Would you recommend adding other metals on top of the platinum pads to improve solderability and wirebonding?
I want to pattern a 1000nm thermal oxide layer with features down to 10 microns. We have successfully used dry etching, but the etch rate is very slow (30nm/min). I believe wet etching with HF could be the solution, but last time we tried we had problems with HF undercutting the photoresist.
Can you recommend a recipe to accurately wet etch a thick layer of SiO2? For instance, photoresist thickness/baking and what formulation of HF to use, ideally with a reference.
Recently, I try to realize a anodic bonding between Si wafer and Pyrex7740 glass, with two intermediate layers-a 2um thickness SiO2 and a 400nm thickness Si3N4.
Can anyone give me some suggestions about the success of this anodic bonding?
There are papers reported about the successful anodic bonding between Si-SiN-SiO, but with the increase of the intermediate layers, especially SiN, will degrade the possibility of successful anodic bonding.
I'm trying to deposit an amorphous carbon layer at 300 ˚C using PECVD with methane and helium as my primary carrier gasses. I've been using a Plasmatherm RF chamber (13.56 MHz) with great success at depositing amorphous silicon, silicon dioxide, and silicon carbide (hydrogenated), but attempts to deposit just carbon (hydrogenated) have all failed at 300 ˚C. However, I can deposit carbon at lower temperatures of 100 ˚C with ease. I'm assuming that the residence time of the carbon ions is either too low in the chamber or the temperature causes any ionized particles that land on the substrate to desorb before they can effectively bond onto the surface. I've tried varying deposition parameters to alleviate these concerns with no success.
Can anyone point me in a good direction to go with depositing at 300 ˚C? Does anyone have experience with this?
I am wondering if it is possible to use pillar array columns for separations other than in the reversed-phase mode? I have found a paper explaining the difficulty of coating the pillar surface with C18 being the small interpillar spaces, and because of the adsorbed water that may cause polymerization (and thus clogging). However, I don't quite understand how this would translate in modifying the pillar surface to suit normal phase, or other modes. As far as my knowledge goes, the silicon forms silicon dioxide spontaneously, and the surface should, therefore, be modified just as easily as silica-based packed columns.
Im using SU8 3050 on stainless steel to create periodic rectangular features. My main issue is that following the development, the widths of the features are larger than in the intended design. My mask is dark field with rectangles of 5mmx 300um wide for the exposure. Under the microscope instead of being 300um, the features appear noticeably larger, around 350um-400um.
To minimize mask contamination Ive been using proximity lithography with a gap of 20um, would this cause such a substantial increase in substrate exposure leading to the larger features?
My fabrication procedure is:
1) 4 minute solvent clean in ultrasonic bath with acetone, methanol, IPA and then RO water, dehydration bake of at least 2 hours
2)Spin SU8-3050 at 2000rpm for 30 s
3)Pre-exposure bake for 30 mins at 115oC
4)Exposure for 50s
5)Post exposure bake gradually increasing from 65oC to 95oC
6)Develop in EC solvent for 8 minutes, wash in IPA
7)Hardening bake for an hour
I was contemplating whether it is possible to overdevelop SU8, but I doubt this is the cause.
My main query, is whether the issue is merely light diffraction due to the use of proximity lithography?
Any suggestions as to why the lines are thicker than intended would be great!
I'm working on patterning hydrogels micro-structures on wafers using UV exposure. It is referred by many papers that by silanizing the wafer, adhesion between the hydrogel and the wafer can be improved. Problem is that wafers become very hydrophobic and are very difficult to wet with hydrogel precursors.
I tried to spin coat PEG-DA (MW 575) and HEMA-DMAEMA on wafers modified with Silane A174. Both compounds quickly evaporated or flowed off wafers....
Any input is appreciated. Thank you!
We are looking for highly accurate and stable low pressure sensor for a new sensor design. We need to have very low temperature effects and high linearity.
Regards Bern Mark
I am looking to outsource production of copper features with micron resolution on polymer substrates. I currently do this myself, but am looking for potential larger scale production.
Hi , my project needs good isolation between copper and graphene, who's thickness should be less than 200nm. As my wafers is gone through many process so its not acceptable in those machines which deposit Sio2 . so is there any alternative material or oxide layer I can use as insulating layer between graphene and copper layer ?
I'm working on an electrochemical biosensor integrated into a microfluidic system. The working and counter electrodes are gold, and the reference electrode is Ag/AgCl.
I'm planning to either immobilize thiolized nucleic acids on the bare gold WE surface, or use 11-mercaptoundecanoic acid SAM method to functionalize the WE surface for EDC-NHS coupling to proteins.
Due to the way the microfluidic device is fabricated, I may need to immobilize the biorecognition probes within closed channels (post-bonding). I also want to functionalize only the WE, while keeping the CE/RE uncoated.
Can anyone guide me on how this can be done?
I am trying to achieve a 2mm thickness of SU8-100. I am applying 3-4 layers (200-250 microns each layer) to achieve this thickness, however, the SiO2 wafer is bowing after baking. After I spin on the SU8, I insert the wafer into an oven set at 65C for 30 minutes and then set the oven to 95C and bake the wafer/SU8 for another 90 minutes.The end result is that the SU8 thickness varies across the wafer, and the last layer is causing the wafer to bow.
I tried making a composite of 10wt% particle loading, mixed and exposed by photolithography but the features though i can view the pattern after post bake but, upon developing everything washes off/ or no sign of it.
When it comes to thin-film which one is more desirable? (Particularly, where the thin film is used as the first layer of a multi-layer thin films fabrication)
1- a film with a higher internal tress and higher Tensile
2-a film with a lower internal tress and lower Tensile
Thank you for your time and help.
I have fabricating su8 chips using su8 100 on the glass substrate. I have tried few times by changing the exposed time, spin coating speed, and even the prebake temperature, but for most chips there always remained some material in tiny patterns which cannot be perfectly removed by developing. I found the development will be stopped after 2hr immersing in su8 developer solution.
Please let me know whether you encountered the same situation and why this happened? Thanks.
My protocol was attached below:
1, preparation the substrate: wash, 120℃ for 10min
2, coating: 500rpms 7s, 1400rpm for 30s
3, prebake: 65℃ 30min, 95℃ 60min
4, UV exposure: 6-8s
5, postbake: 65℃ 15min, 95℃ 20min
6, development, immersing for 2-3hr(MicroChem Developer)
I am trying to fabricate free standing PMMA micro structures on Silicon substrate, which requires isotropic, selective silicon etching leaving large undercut. I've tried wet etching with KOH, however the selectivity was poor. Reactive ion etching with SF6+C4H8 yields better results, but longer etching time towards desired undercut (~20um) partially destroys PMMA.
Could someone please suggest different recipe with RIE or an alternate approach? (XeF2 would have been promising option, unfortunately we don't have it)
Thank you very much.
We have a Faraday cup in the beam line. This cup can be moved back and forth in a single axis. We measure diameter and uniformity of He ion beam by measuring the current induced in the faraday cup at different positions. The He ion beam itself can be moved with the help of deflectors.
When the faraday cup is at -72V bias:
The cup gives us normal reading (which is about -0.8 to -1.2 nA current) in first half of the beamline but when it reaches approximately the middle of the beamline, the current value drops and switches polarity (it shows about +0.1 nA current), which remains the case thoughout the second half of the beamline. When we move the cup back to the first half of the beamline, it switches back to normal values.
When the cup is at +72V bias or is grounded:
In this case, the problem is exactly reversed. The cup gives normal but slightly lower and positive reading (which is about +0.4 to +1 nA) in second half of the beam, but gives Zero reading in the first half of the beam.
At negative bias of the cup: When we move the whole ion beam with help of deflectors to the first half of the beamline, we have a normal reading. Which means the problem is with the position and not the beam. We have also changed Ammeter, which gives us the same result. Also, we know from resist exposure experiments that there is no blockage of the beam.
The beamline is under vacuum for the experiments. The wire connections to the faraday cup are covered with copper tape so that the plastic covering of wires doesn't accumulate charge. This copper tape is touching the faraday cup body and is grounded. The wires seem to hang a little and might touch the beamline chamber when the cup is moved to the center of the beam line, but since the wires are covered with copper tape (which is grounded) we are not sure if that is the problem.
Kindly help us out. If possible, also suggest some experiments to find out more about the problem.
Edit: The beam is continues and has Gaussian profile
We have developed a torsional micro-gyroscope using UV-LIGA process. The device has been tested for resonator characteristics using LDV. However, at present, we do not have rate table characterization facility (both the equipment and sensing circuit) with us. Can someone help us to get this characterization done?
Hi! Im using a contact lithography machine to process negative type dryfilm. I would like to ask if there are any existing methods for changing the slope of the resist similar to that of a positive resist without using a new resist entirely.
So far I have tried with changing exposure gaps and increasing exposure doses, but the best I seem to get is a an angle nearing 90 degrees with some undercuts.
Thank you in advance for your help!
I had already prepared MOS2 by hyrdothermal method. The amount i got is very little. But, I need to prepare few grams. Kindly, suggest your valuable ideas. THANK YOU