[labnetwork] Some info on HfO2 precursors

[Frank Flack]

Hi all,

We use TDMAH in our Fiji G2 and have not had delivery issues though we do keep the cylinder at elevated temps when idle.

Is there a separate ALD group mail or just an informal mailing list?  Please add me, if so!

Thanks,
Frank


Frank S. Flack

University of Wisconsin Centers for Nanoscale Technology

Rm. 3120 Engineering Centers Bldg.

1550 Engineering Drive

Madison, WI 53706

________________________________
From: labnetwork <labnetwork-bounces at mtl.mit.edu> on behalf of Martin, Michael <michael.martin at louisville.edu>
Sent: Tuesday, August 18, 2026 4:35 PM
To: Network Fab <labnetwork at mtl.mit.edu>
Cc: Stefan Myhajlenko <myhajlenko at asu.edu>; dleber <dleber at vt.edu>; Yu <ywu387 at gatech.edu>; a-dhote <a-dhote at northwestern.edu>; Chen, Zhi D. <zhi.chen at uky.edu>; Gary <gary.spinner at ien.gatech.edu>; Bill Mitchell <mitchell at ece.ucsb.edu>; Morris, JD <james.morris.3 at louisville.edu>; Tony Whipple <whipp003 at umn.edu>
Subject: [labnetwork] Some info on HfO2 precursors

Hi Labnetwork:
   I wanted to summarize some advice from our informal ALD working group (formerly NNCI ALD group I think)  about HfO2 precursors so that this info will be in the labnet archive and available in the Labnetwork chatbot.

"I see there are something like 4 Hf precursors that folks have used in the literature.


  1.
TEMAHf   (Tetrakis(ethylmethylamido)hafnium(IV),(EtMeN)4Hf)
  2.
Tris(dimethylamido)cyclopentadienyl Hafnium, HfCp(NMe2)3 (HyALD)
  3.
Tetrakis(dimethylamido)hafnium(IV) [TDMAH]
  4.
And a chlorinated Hf compound.

We have some limited experience with TDMAH but Beneq suggests TEMAHf or HyALD is more stable.  What is your go-to Hf precursor? "

Tony Whiple from Minnesota pointed out that they:
"use Tetrakis(dimethylamido)hafnium(IV) [TDMAH]  in all of our ALD systems, Savannah, Lesker, Fiji. We continue to keep with the same precursors as users have set processes for that.

We have had a few issues with using this, mainly the random end of service of the precursor.
The causes of the cylinder going bad ( not able to pulse material, while the cylinder is only half empty ) can at times be assigned to the cylinder heat being turned off and going to room temperature.  After reheating to the correct temperature, there is a chance the cylinder will go bad.  We have had this happen only a few times.  To keep this from happening, we avoid having the cylinders cool off."

Evidently others (Mac from Harvard and Bangzhi from PSU) have had similar problems with TDMAH- incidentally this is a big problem with the SnO2 precursor TDMASn.  Mac suggests loading only a small amount of TDMAH at a time, and Bangzhi suggested that sometimes cycling the manual valve to the bottle may free up the delivery line.

My inclination based on this advice is to try the TEMAHf   (Tetrakis(ethylmethylamido)hafnium(IV),(EtMeN)4Hf) option given that we may not have super high throughput so a stable precursor might be important in our case and Beneq has provided a starting recipe.  Generally, my impression is that the chlorinated precursors can cause problems with the plumbing and pumps since the reaction yields HCl .

I'd love to hear any other advice people may want to share on this process and precursors.


Regards,

   Michael Martin, Ph.D.


Manager, Micro/Nano Technology Center

University of Louisville

(502) 552-1945

Web page<https://urldefense.com/v3/__https://louisville.edu/micronano__;!!Mak6IKo!N8o4RHDHfZacpJb-Oui9qE1x7LVmmd6MUertGh2ziQiarKXk5WMjBmo5a5JxaVo8hn5OzokSTotpdu1zOyEUhdbQX9Qgmpc$> Instagram<https://urldefense.com/v3/__https://www.instagram.com/micronanolouisville/__;!!Mak6IKo!N8o4RHDHfZacpJb-Oui9qE1x7LVmmd6MUertGh2ziQiarKXk5WMjBmo5a5JxaVo8hn5OzokSTotpdu1zOyEUhdbQOAR6w08$> Facebook<https://urldefense.com/v3/__https://www.facebook.com/MNTCUOFL/__;!!Mak6IKo!N8o4RHDHfZacpJb-Oui9qE1x7LVmmd6MUertGh2ziQiarKXk5WMjBmo5a5JxaVo8hn5OzokSTotpdu1zOyEUhdbQ9Af_AVE$>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mtl.mit.edu/pipermail/labnetwork/attachments/20260819/b5f7102c/attachment.html>