<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<meta name="Generator" content="Microsoft Word 15 (filtered medium)">
<!--[if !mso]><style>v\:* {behavior:url(#default#VML);}
o\:* {behavior:url(#default#VML);}
w\:* {behavior:url(#default#VML);}
.shape {behavior:url(#default#VML);}
</style><![endif]--><style><!--
/* Font Definitions */
@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
@font-face
{font-family:Aptos;
panose-1:2 11 0 4 2 2 2 2 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0in;
font-size:12.0pt;
font-family:"Aptos",sans-serif;
mso-ligatures:standardcontextual;}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:#467886;
text-decoration:underline;}
span.EmailStyle17
{mso-style-type:personal-compose;
font-family:"Aptos",sans-serif;
color:windowtext;}
span.apple-converted-space
{mso-style-name:apple-converted-space;}
.MsoChpDefault
{mso-style-type:export-only;}
@page WordSection1
{size:8.5in 11.0in;
margin:1.0in 1.0in 1.0in 1.0in;}
div.WordSection1
{page:WordSection1;}
--></style>
</head>
<body lang="EN-US" link="#467886" vlink="#96607D" style="word-wrap:break-word">
<div class="WordSection1">
<div align="center">
<table class="MsoNormalTable" border="0" cellspacing="0" cellpadding="0" width="600" style="width:6.25in">
<tbody>
<tr>
<td style="padding:0in 0in 0in 0in">
<p class="MsoNormal"><span style="font-size:13.5pt;font-family:"Arial",sans-serif;color:black"><img width="600" height="171" style="width:6.25in;height:1.7812in" id="Picture_x0020_3" src="cid:image002.png@01DBDF76.78BDA0F0" alt="Dissertation Defense Announcement at the Cullen College of Engineering"></span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><o:p></o:p></span></p>
<div align="center">
<table class="MsoNormalTable" border="0" cellspacing="0" cellpadding="0" style="background:white">
<tbody>
<tr>
<td style="padding:30.0pt 15.0pt 7.5pt 15.0pt">
<p class="MsoNormal" align="center" style="text-align:center"><b><span style="font-size:18.0pt;font-family:"Calibri",sans-serif;color:#C8102E">Plasma-Assisted Atomic Layer Etching of Si in Cl and Br-Containing Plasma</span></b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><o:p></o:p></span></p>
<p class="MsoNormal"><b><span style="font-size:18.0pt;font-family:"Calibri",sans-serif;color:#C8102E"> </span></b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><o:p></o:p></span></p>
<p class="MsoNormal" align="center" style="text-align:center;line-height:15.0pt">
<b><span style="font-family:"Arial",sans-serif;color:black">Qinzhen Hao</span></b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><o:p></o:p></span></p>
<p class="MsoNormal" align="center" style="text-align:center;line-height:15.0pt">
<span style="font-size:13.5pt;font-family:"Calibri",sans-serif;color:black"> </span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><o:p></o:p></span></p>
<p class="MsoNormal" align="center" style="text-align:center;line-height:16.5pt">
<span style="font-size:11.0pt;font-family:"Arial",sans-serif;color:black">June 17, 2025; 10:00 AM – 1:00 PM</span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><o:p></o:p></span></p>
<p class="MsoNormal" align="center" style="text-align:center;line-height:16.5pt">
<b><span style="font-size:11.0pt;font-family:"Arial",sans-serif;color:black"> </span></b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><o:p></o:p></span></p>
<p class="MsoNormal" align="center" style="text-align:center;line-height:16.5pt">
<b><span style="font-size:11.0pt;font-family:"Arial",sans-serif;color:black">Location:</span></b><span class="apple-converted-space"><span style="font-size:11.0pt;font-family:"Arial",sans-serif;color:black"> </span></span><span style="font-size:11.0pt;font-family:"Arial",sans-serif;color:black">Mechanical
Engineering Conference Room 202</span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><o:p></o:p></span></p>
<p class="MsoNormal" align="center" style="text-align:center;line-height:16.5pt">
<b><span style="font-size:11.0pt;font-family:"Arial",sans-serif;color:black">Microsoft Teams Link:<span class="apple-converted-space"> </span></span></b><span style="font-size:11.0pt;font-family:"Arial",sans-serif;color:black"><a href="https://urldefense.com/v3/__https://teams.microsoft.com/l/meetup-join/19*3ameeting_NDMwYTk3ZDktZDgyZi00YjdjLWFmOTgtYThlZjU0MWJkZTZm*40thread.v2/0?context=*7b*22Tid*22*3a*22170bbabd-a2f0-4c90-ad4b-0e8f0f0c4259*22*2c*22Oid*22*3a*220e3ff7cf-7965-4066-aadb-29ebe11a7c26*22*7d__;JSUlJSUlJSUlJSUlJSUl!!LkSTlj0I!D8c8xfX62RVwwb8r2L4aQbQyU3zv3obIHy1MxeR9c44eBI7UhED6msd3bLkvPvBrqS-40WibhWf5Ju6sKrhezY5X$" title="https://teams.microsoft.com/l/meetup-join/19%3ameeting_NDMwYTk3ZDktZDgyZi00YjdjLWFmOTgtYThlZjU0MWJkZTZm%40thread.v2/0?context=%7b%22Tid%22%3a%22170bbabd-a2f0-4c90-ad4b-0e8f0f0c4259%22%2c%22Oid%22%3a%220e3ff7cf-7965-4066-aadb-29ebe11a7c26%22%7d"><span style="color:#954F72">https://teams.microsoft.com/l/meetup-join/19%3ameeting_NDMwYTk3ZDktZDgyZi00YjdjLWFmOTgtYThlZjU0MWJkZTZm%40thread.v2/0?context=%7b%22Tid%22%3a%22170bbabd-a2f0-4c90-ad4b-0e8f0f0c4259%22%2c%22Oid%22%3a%220e3ff7cf-7965-4066-aadb-29ebe11a7c26%22%7d</span></a></span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><o:p></o:p></span></p>
<p class="MsoNormal" style="line-height:16.5pt"><b><span style="font-size:11.0pt;font-family:"Arial",sans-serif;color:black"> </span></b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><o:p></o:p></span></p>
<p class="MsoNormal" align="center" style="margin-bottom:12.0pt;text-align:center;line-height:16.5pt">
<b><span style="font-family:"Arial",sans-serif;color:black">Committee Chair:</span></b><span style="font-size:10.5pt;font-family:"Arial",sans-serif;color:black"><br>
</span><span style="font-size:11.0pt;font-family:"Arial",sans-serif;color:black">Vincent Donnelly, Ph.D.</span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><o:p></o:p></span></p>
<p class="MsoNormal" align="center" style="text-align:center;line-height:16.5pt">
<b><span style="font-family:"Arial",sans-serif;color:black">Committee Members:</span></b><span style="font-size:11.0pt;font-family:"Arial",sans-serif;color:black"><br>
Demetre Economou, Ph.D.<span class="apple-converted-space"> </span><b>|</b><span class="apple-converted-space"> </span>Michael Nikolaou, Ph.D.<span class="apple-converted-space"> </span><b>|</b><span class="apple-converted-space"> </span>Mehmet Orman, Ph.D.<span class="apple-converted-space"> </span><b>|</b></span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><o:p></o:p></span></p>
<p class="MsoNormal" align="center" style="margin-bottom:15.0pt;text-align:center;line-height:16.5pt">
<span style="font-size:11.0pt;font-family:"Arial",sans-serif;color:black">Qiang Wang, Ph.D.</span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><o:p></o:p></span></p>
</td>
</tr>
<tr>
<td style="padding:0in 15.0pt 15.0pt 15.0pt">
<p class="MsoNormal" style="margin-bottom:11.25pt;line-height:16.5pt"><b><span style="font-family:"Arial",sans-serif;color:#C8102E">Abstract</span></b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><o:p></o:p></span></p>
<p class="MsoNormal" style="text-align:justify;line-height:17.6pt"><span style="font-family:"Times New Roman",serif;color:black">Atomic-scale precision in silicon plasma etching is indispensable for the fabrication of next-generation three-dimensional (3D)
semiconductor devices. Yet plasma-assisted atomic layer etching (PA-ALE) continues to be limited by low throughput, poor self-limiting behavior, and an incomplete understanding of surface kinetics. My research tries to address these challenges through a systematic
study performed in a modified continuous-wave (CW) inductively coupled plasma (ICP) reactor. Time-resolved, in-situ optical emission spectroscopy (OES) is established as a quantitative tool of surface reactions during ALE cycles employing Cl₂, HBr, and Br₂
chemistries. The measurements show that SiCl₂ and SiCl constitute the primary products in Cl₂-based ALE. Two process sequences—gas dosing and plasma gas dosing—are explored and compared: pseudo-self-limiting behavior emerges in HBr plasma gas dosing cycles,
whereas Br₂ have greater Br surface coverage and higher etch rates under gas-dosing conditions compared to HBr. Because HBr have high sticking coefficients, gas residence time experiments reveal a two-stage purge consisting of a volume-limited decay followed
by wall retention limited desorption; wall passivation via temperature control, Ar/SF₆/O₂ conditioning, and increased total gas flow rate substantially shortens the wall retention time.</span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><o:p></o:p></span></p>
<p class="MsoNormal" style="text-align:justify;line-height:17.6pt"><span style="font-family:"Times New Roman",serif;color:black">Moreover, fast-pulsed substrate bias with continuous gas flow effectively decouples the dose and etch steps, eliminating mechanical
gas-pulsing system and markedly increasing throughput. Simultaneously tracking the ALE percentage and the bias-on integrated intensity of primary products’ OES lines enables evaluation of both self-limiting fidelity and etch rate. Collectively, this work elucidates
the primary reaction products and pathways in Si ALE for multiple halogen chemistries, delivers robust, high-throughput recipes that achieve sub-nm precision with cycle times below 2 s, and provides diagnostic and hardware guidelines transferable to other
ICP tools. These advances are promising to expedite the transition of PA-ALE from lab to high-volume manufacturing, making a further step to achieve damage-free patterning of sub-10 nm features for future logic and memory devices.</span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><o:p></o:p></span></p>
</td>
</tr>
<tr>
<td style="padding:0in 15.0pt 15.0pt 15.0pt">
<p class="MsoNormal" style="margin-bottom:11.25pt;line-height:16.5pt"><b><span style="font-family:"Arial",sans-serif;color:#C8102E"> </span></b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><o:p></o:p></span></p>
</td>
</tr>
</tbody>
</table>
</div>
</td>
</tr>
<tr>
<td style="padding:0in 0in 0in 0in">
<p class="MsoNormal"><span style="font-size:13.5pt;font-family:"Arial",sans-serif;color:black"><img border="0" width="600" height="82" style="width:6.25in;height:.8541in" id="Picture_x0020_2" src="cid:image003.png@01DBDF76.78BDA0F0" alt="Engineered For What's Next"></span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><o:p></o:p></span></p>
</td>
</tr>
</tbody>
</table>
</div>
<p class="MsoNormal" style="caret-color: rgb(33, 33, 33);font-variant-caps: normal;orphans: auto;text-align:start;widows: auto;-webkit-text-stroke-width: 0px;word-spacing:0px">
<span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#212121"> <o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
</body>
</html>