For example how can we control over etching or high undercutting?
LAO (Local Anodic Oxidation)
Hi Arash,
First of all, what is the thickness of your SOI layer ?...i mean silicon one.
Meanwhile here it is some indications:
-KOH etch silicon but also the oxide of hardmask and by the way the oxide of the burried oxide layer in the SOI structure. In fact the best HM should be Nitride. Nevertheless the only mean to increase selectivity towards oxide layers (top = HM and bottom =burried oxide layer) should be to lower as much as possible your temperature and KOH concentration (for instance: 5-10% KOH at ambiant T°).
-in another side the LAO film HM should be well defined; I mean edge must be well define to avoid Si roughness on profile sides or more precisely to avoid irregular undercutting....and by the way a final design not well defined. This irregular undercutting can be due to the definition of the mask but also to its thickness. For instance: a very thin HM(it is the case here) coupled to a high undercutting can make the mask collapse and by the way slowdown the etching in this localised place.
Of course all this depends on what you are looking fro exactly!....
Regards
Mohamed
Hi Mohamed, thanks for reply and you time, I agree with you. The Si thickness is about 100nm, we tested different temperature in etching but still didnt get good result. I think the uniformity of the oxide layer is important which is in contact mode we have a limitation for applying voltage. Moreover the diffusion effect during exposure does not let to reach good definition..Please tale a look at this article and share your opinion about it, look at the take a look at this article of mine, "Impact of KOH Etching on Nanostructure Fabricated by Local Anodic Oxidation Method" and specially figure 10, for our case (LAO oxide 3nm thickness) there is difference with standard angle in anisotropic etching...
Article Impact of KOH Etching on Nanostructure Fabricated by Local A...
Hi Arash.
I will take more time for the article reading but I rapidly took a look to the part dealing With the angle measured on figure 10. My first question concerns the way the measurement is performed...It seems that it is a tilted Top View... Did the measure has been corrected as regards to the tilt?... other questioni:... did you see a difference in angle between the Top & the bottom ofthe silicon wall / profile?
Regards
Mohamed
Dear Mohamed,
Thank you for your time. The measurment performed by HRTEM. We got the exact length of the trapezoidal shape of nanowire's profile in the figure which leads to a simple trigonometry calculation for the angle. In fact the TEM itself gave us the angle which was 49 but we rechecked it with the exact geometrical measurements given by HRTEM and we came up with 54.9.
Regards
Arash
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