[Libre-silicon-devel] Uncertainty: DMD chips and 420nm

[Ferenc Éger]

Hello Everyone,

HPR504 [1] (used back in HKUST) is usable for this purpose, as well as 
any other resists for g-line (436nm) exposure. As for developing HPR504, 
the HKUST recipes mention FHD-5 [2], which is essentially TMAH.

[1] https://people.rit.edu/deeemc/reference_13/photoresists/HPR-504 Data 
Sheet.pdf

[2] http://mfz140.ust.hk/msds/FHD-5 MSDS.pdf

Regards,

Ferenc


On 13/08/2021 16:04, David Lanzendörfer wrote:
> Good morning Dilek ^^
>
> Fantastic! Thanks so much!
> I will put those resists onto the wiki page as examples for resists to use,
> and will mention that we'd be glad about reports of results using alternative
> resists within that wave length range.
>
> And yes. I already had a discussion about the toxic chemical waste a while
> ago, where I made the usual joke that I'd follow "all the laws and regulations
> of the PRC", when I was told that I'd be in Portugal now and they'd have laws
> making it illegal to flush it down the toilet xD
>
> I already checked, where the collection centers are here in Portugal and what
> chemicals are actually legal to buy as a private citizen.
>
> Cheers,
> David
>
> On Friday, August 13, 2021 2:49:45 PM WEST Dilek Isik Akcakaya wrote:
>> Good morning,
>>
>> Greyscale PR is not a good option overall. It is meant for a different
>> process. We will go with regular resists AZ series probably due to their
>> process being cheaper. We can look for others too. High contrast resists
>> are better at giving vertical sidewall.
>>
>> AZ1512 1.2um thick positive 310-440 nm abs
>> AZ9260 5-20 um thick positive 365-435 nm.
>>
>> But we do not need to state these at the moment do we? We can basically say
>> that any PR absorbing in this range would be sufficient to work with. We
>> are not adbertising products after all :)
>>
>> Semiconductor manufacturing chemicals are usually highly toxic to person and
>> aquatic life. I see youtubers being very brave about their use without any
>> fume hoods etc. I believe we will need to prepare a safety notice for
>> people who are interested in the fieldnand have no idea what they are
>> doing. You can not pour thess chems into the drain they need to be
>> collected and sent to facilities for neutralization. Some cause cancer...
>> Some can kill you with a drop.
>>
>> Thank you,
>>
>> Dilek
>>
>> Sent from ProtonMail mobile
>>
>> -------- Original Message --------
>>
>> On Aug 13, 2021, 6:15 AM, David Lanzendörfer wrote:
>>> Hi Dilek
>>>
>>> About the choice of the PR:
>>> I just went for one which has a sufficient energy absorption within the
>>> visible UV range still tolerated by the inexpensive DMD chip chosen.
>>> Now that you pointed out the issue with TMAH I realize that my choice of
>>> PR
>>> wasn't the best.
>>> Can you suggest alternatives which do not require super toxic and
>>> dangerous
>>> developers but still work within the specified UV range of 420nm - 450nm?
>>> I'm aware how dangerous TMAH is, it even etches silicon, which I observed
>>> myself while doing some tests for the ultra low tech process flow variant,
>>> where I used it to etch the trench isolation.
>>> The absorption wave length was basically the only criteria which led me to
>>> suggest this specific resists, but as I've said, if we could collect a
>>> list of alternative resists delivering sufficient results in the above
>>> mentioned range, we HAVE TO put it onto our wiki page as well.
>>>
>>> About the certainty of being able to reproduce 25 um (featuresize 50um ->
>>> lambda 25um):
>>> In order to be sure, we've got to build a prototype and test it :-)
>>>
>>> Cheers,
>>> David
>>>
>>> On Friday, August 13, 2021 8:03:33 AM WEST Dilek Isik Akcakaya wrote:
>>>> Hi All, David,
>>>>
>>>> I see that you selected a greyscale PR for photolithography, it uses TMAH
>>>> based developers I do not know the range of other developers it can make
>>>> use of. Can we list them? This series of PR are foreign to me. I used
>>>> Shipley, AZ etc. You must not buy and use TMAH based developers at home
>>>> labs due to safety reasons it is extremely toxic! Second chemical I will
>>>> beware of is HF in the same way in a home environment.
>>>>
>>>> Second,
>>>> What is the reason for going for a grayscale PR and not a regular one?
>>>>
>>>> Third,
>>>> The UV range depends on the PR we will be using, the smaller the
>>>> wavelength, more precise will be the features if we can use the right
>>>> optical system of course (De Broglies eqn.). Because I am new to the
>>>> project please let me know why we decide don this set of PRs.
>>>>
>>>> As per UV range of the DLP once again this depends on the PRs to be used
>>>> and because DLP works by reflection, you may loose power due to
>>>> reflectance, absorption and other optical phenomena therefore I think we
>>>> need to be as precise as possible with our selections.
>>>>
>>>> Let me point out:
>>>> The rail system precision+ DLP resolution (not the pixel size)
>>>> as an end result of multiple selections such as good focus etc+ PR
>>>> thickness+ Development time + Light source wavelength + overlay
>>>> reproducibility = approximately OUR RESOLUTION.
>>>>
>>>> With current selections are we sure we will be able to reproduce 50 um
>>>> features and have a good overlay if we need a second layer alignment on
>>>> top?
>>>>
>>>> Thank you,
>>>>
>>>>
>>>>
>>>>
>>>> Sent with ProtonMail Secure Email.
>>>>
>>>> ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
>>>>
>>>> David Lanzendörfer <leviathan at libresilicon.com> 11 Ağustos 2021 Çarşamba
>>> saat 12:51 tarihinde yazdı:
>>>>> Hi Dilek, hi list
>>>>>
>>>>> Sorry again about the downtime of the infrastructure during the day
>>>>> yesterday.
>>>>>
>>>>> The infrastructure of the data center I've got my rack server in was
>>>>> down.
>>>>>
>>>>> Now to the topic:
>>>>>
>>>>> I've started writing down the BOM and I'm not sure whether 420 nm UV
>>>>> already
>>>>>
>>>>> has too much energy, although the data sheet of the DMD chip says it's
>>>>> ok
>>>>> to
>>>>>
>>>>> be operated until 400nm.
>>>>>
>>>>> Here's the BOM:
>>>>>
>>>>> https://redmine.libresilicon.com/projects/maskless-lithography/wiki
>>>>>
>>>>> It would be cool to get feedback on that from Texas Instruments.
>>>>>
>>>>> Cheers
>>>>>
>>>>> David
>>>>>
>>>>> -----------------------------------------------------------------------
>>>>> ---
>>>>> -----------------------------------------------------------------------
>>>>> ---
>>>>> -----------------------------------------------------------------------
>>>>> ---
>>>>> -----------------------------------------------------------------------
>>>>> ---
>>>>> -----------------------------------------------------------------------
>>>>> ---
>>>>> -----------------------------------------------------------------------
>>>>> ---
>>>>> -----------------------------------------------------------------------
>>>>> ---
>>>>> ------------------------
>>>>>
>>>>> (\__/)
>>>>>
>>>>> (='.'=) This is Ninja Bunny.
>>>>>
>>>>> (")_(")
>>>>>
>>>>> Copy and paste Bunny into your
>>>>>
>>>>> signature to help him gain world domination
>>> --
>>> (\__/)
>>> (='.'=) This is Ninja Bunny.
>>> (")_(")
>>> Copy and paste Bunny into your
>>> signature to help him gain world domination
>