<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto">That etchant sounds correct. Clawson usually works. <div><br><div>If it’s not etching at all, then there is a residual layer left from previous etches. <div>Things I would do in your situation:</div><div><br></div><div>-Observe surface wetting before/during each wet etch. If surface is slightly hydrophilic, then wet etchants may not attack (or be significantly slowed down in) smaller etching regions due to caught air bubbles. </div><div>Common remedy to this is O2 plasma RIE to make surface hydrophilic. For us, 15sec in this O2 Asher does the trick (want ion bombardment, not Ozone for example)</div><div><a href="https://wiki.nanotech.ucsb.edu/wiki/index.php/Ashers_(Technics_PEII)">https://wiki.nanotech.ucsb.edu/wiki/index.php/Ashers_(Technics_PEII)</a></div><div>Nothing wrong with just doing an O2 plasma before any of these wet etches since they’re all usually oxidation-reduction (so generating an oxide is acceptable).</div><div><br></div><div>- overetch the previous wet etches, </div><div>inspect depth change and/or color change at every step. If etches are highly selective, should see identical uniform color in etched regions across the sample. Look closely by eye, but also microscope. Sometimes can observe during the etch itself, through beaker.</div><div>Use same microscope/settings each time to ensure same color, take photos for reference. </div><div>In extreme cases I would also save known etched pieces in order to check color against my sample (to ensure surface had exposed the material I expected), although this is dependent on the absorption of visible light in the materials being observed, so beware of optical interference. </div><div><br></div><div><div dir="ltr"><div><span class="Apple-style-span" style="-webkit-tap-highlight-color: rgba(26, 26, 26, 0.294118);">-- Demis</span></div><div><br></div></div><div dir="ltr"><br><blockquote type="cite">On Jan 7, 2020, at 19:58, McWilliams, Scott <mcwilliamss@mail.smu.edu> wrote:<br><br></blockquote></div><blockquote type="cite"><div dir="ltr">
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Thank you all for your replies, I will check to see if the peroxide is the issue. I did etch the nitride with BOE, so didn’t dry etch it. After the BOE etch I stripped off the photoresist with solvents. For these wafers, I need to remove an InP layer and
then an InGaAsP layer before etching the InGaAlAs. Regards, Scott<br>
<br>
<div dir="ltr">Sent from my iPhone</div>
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<blockquote type="cite">On Jan 7, 2020, at 4:38 PM, Fouad Karouta <fouad.karouta@anu.edu.au> wrote:<br>
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<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Hi Scott,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Usually the solution you mentioned should be able to etch the material. You may consider using smaller amount of water.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Do you have any other layers on top of the InGaAlAs layer?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Note H2O2 solutions should be made fresh every time of usage.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">I used a same solution to etch GaAs/AlAs at RT. Also we did sometime at 0°C.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">CH4/H2 process will etch very slowly Al containing materials.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Hope this helps,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Fouad Karouta<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span lang="EN-US">From:</span></b><span lang="EN-US"> labnetwork-bounces@mtl.mit.edu <labnetwork-bounces@mtl.mit.edu>
<b>On Behalf Of </b>McWilliams, Scott<br>
<b>Sent:</b> Wednesday, 8 January 2020 7:32 AM<br>
<b>To:</b> labnetwork@mtl.mit.edu<br>
<b>Subject:</b> [labnetwork] wet etching InGaAlAs<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span lang="EN-US">Hello All, <o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">I’m processing some wafers and need to wet etch layers of InGaAlAs of various compositions (Al</span><span lang="EN-US" style="font-size:8.0pt">x
</span><span lang="EN-US">values of x = 0.48 to 0.27). I pulled a reference from the A.W. Clawson III-V etch reference guide that H3PO4/H202/H20 1:1:10 should etch this material, but it is not etching. The referenced paper does not provide the etchant temperature.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">I suspect that I need to perform a surface etch of some type before etching the InGaAlAs. We do have the limitation that our current mask is 600 angstroms of silicon nitride, so we may be prohibited from performing HF
containing surface etches.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Does anyone have experience with this material and a recommended surface clean? Is there a better etchant to use? Has anyone attempted to dry etch this material with a CH4/H2 process?<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Thank you, Scott<o:p></o:p></span></p>
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