<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=us-ascii">
<style type="text/css" style="display:none;"> P {margin-top:0;margin-bottom:0;} </style>
</head>
<body dir="ltr">
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
Pallavi,</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
<br>
</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
Grass can be the result of the following -</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
<ol>
<li> Recipe conditions - balance between etch & deposition that can be controlled by recipe parameters. </li><li>Chamber condition - If the chamber is dirty doing plasma clean will help. Sometimes, wet clean of the chamber may be required to recover the chamber.</li><li>Micromasking - If there is any sputtering from the mask of metal masks are used, incomplete etch of the hard mask if it is used, resist scum left behind after litho, insufficient breakthrough, etc.</li></ol>
<div>I would suggest doing a qualification run with patterned Silicon wafer to verify the machine condition first and see how it compares to the normal times to eliminate equipment / chamber condition related issues first followed by troubleshooting of the
wafer processing. </div>
<div><br>
</div>
<div>Regards,</div>
<div><br>
</div>
<div>Usha</div>
<div><br>
</div>
<div><br>
</div>
</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
<br>
</div>
<div id="appendonsend"></div>
<hr style="display:inline-block;width:98%" tabindex="-1">
<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> labnetwork-bounces@mtl.mit.edu <labnetwork-bounces@mtl.mit.edu> on behalf of Pallavi Sharma <pnsharma@unm.edu><br>
<b>Sent:</b> Monday, July 27, 2020 9:02 AM<br>
<b>To:</b> labnetwork@mtl.mit.edu <labnetwork@mtl.mit.edu><br>
<b>Subject:</b> [labnetwork] Deep Reactive Ion Etch Problems</font>
<div> </div>
</div>
<style type="text/css" style="display:none">
<!--
p
{margin-top:0;
margin-bottom:0}
-->
</style>
<div dir="ltr">
<div style="color:rgb(0,0,0); font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt">
<span>Hello all,</span></div>
<div style="color:rgb(0,0,0); font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt">
<span><br>
</span></div>
<div style="color:rgb(0,0,0); font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt">
<span>I am having problem with anisotropic etching of silicon by Deep Reactive ion etch. Grass or black silicon is the issue all the time, attaching some of the SEM pictures of the sample. Every recipe I tried to fine tune result in grass formation, even as
the process initiates in tool wafer surface starts to turn brown and ultimately black. I tried varying SF6 gas flow, Bias power, Substrate temperature but every time I see is highly dense grass with no clean surface. </span></div>
<div style="color:rgb(0,0,0); font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt">
<span>Any help will be greatly appreciated.</span></div>
<div style="color:rgb(0,0,0); font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt">
<span><br>
</span></div>
<div style="color:rgb(0,0,0); font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt">
<span>Thank you,<br>
Pallavi</span></div>
<div style="color:rgb(0,0,0); font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt">
<span><br>
</span></div>
</div>
</body>
</html>