I'm trying to make a sacrificial layer on a glass substrate. I'll deposit gold on top of it and do lithography on it to write some structures. I have other plans with it afterwards. I'm facing difficulties during removal of the resists I use for lithography.
I used PVA and PMMA so far for the sacrificial layer. For e-beam resist I used ANR7520. PVA can't be used with RIE so I did KI/I2 etching but it reacts with PVA so I dropped the idea. While using PMMA I did Ar plasma etching and O2 for removing gold and 7520 respectively. But it also removes PMMA too. Please help.
Hello Siddhesh.
You need to provide more detail about the feature dimensions and the final desired stack composition (and thicknesses) in order for a refined answer.
Have you considered using a Cr layer? This is a very popular choice for sacrificial layers as it also provides good ahesion between a range of materials.
I have attached a fantastic paper outlining etch rates and selectivities for a range of etchants. I have also found BYU's microprocessing resources highly useful:
http://www.cleanroom.byu.edu/processes.phtml
Kind regards,
Jules
http://thayer.dartmouth.edu/microeng/processing/LocalAccess/JMEMSEtchRates2(2003).pdf
Hi Dr. Jules,
Thanks for the link. I'll take a look at it.
I tried an 900 nm thick layer of PMMA and 100 nm thick layer of Gold. Later the gold layer will be coated with another material and the composite film is to be taken out by dissolving the sacrificial layer. The latter material is not a problem because it is resilient to many chemicals and comes into picture only after etching process. The resist layers used for lithography were 100nm thick each. So I thought there shouldn't be much problem when the PMMA is exposed after the gold is gone (only metamaterial left). Now we are trying to increase the thickness of bottom layer.
I'll consider Cr too.
Thanks,
Siddhesh
What is this 'other material' that you want to put on top to remove the gold? That will limit the choice of etchants that could be used to remove the sacrificial layer, and therefore it limits your choices for which sacrificial layer you could use.
Maybe you could also consider phosphosilicate glass (spin on?) as a sacrificial layer, it should resist oxygen plasma, and can be etched quickly with HF solution, which should not attack your gold (however it will attack your glass substrate).
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