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Hi Labnetwork: </div>
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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. </div>
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"I see there are something like 4 Hf precursors that folks have used in the literature. </div>
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TEMAHf (Tetrakis(ethylmethylamido)hafnium(IV),(EtMeN)4Hf) </div>
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Tris(dimethylamido)cyclopentadienyl Hafnium, HfCp(NMe2)3 (HyALD)</div>
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Tetrakis(dimethylamido)hafnium(IV) [TDMAH]</div>
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And a chlorinated Hf compound. </div>
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We have some limited experience with TDMAH but Beneq suggests TEMAHf or HyALD is more stable. What is your go-to Hf precursor? " </div>
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Tony Whiple from Minnesota pointed out that they:</div>
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"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. </div>
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We have had a few issues with using this, mainly the random end of service of the precursor.<br>
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." </div>
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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. </div>
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My inclination based on this advice is to try the <span style="color: rgb(0, 0, 0);">
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 . </span></div>
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I'd love to hear any other advice people may want to share on this process and precursors. </div>
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<p style="direction: ltr; margin-top: 0px; margin-bottom: 0px;"><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">Regards,</span></p>
<p style="direction: ltr; margin-top: 0px; margin-bottom: 0px;"><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);"> Michael Martin, Ph.D.</span></p>
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<p style="direction: ltr; margin-top: 0px; margin-bottom: 0px;">Manager, <span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
Micro/Nano Technology Center</span></p>
<p style="direction: ltr; margin-top: 0px; margin-bottom: 0px;"><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">University of Louisville</span></p>
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