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delayer:wet [2018/01/21 05:47] – mcmasterdelayer:wet [2025/09/02 20:32] (current) – [Determining sample thickness] Add archive.org link for dead SiO2 colour chart philpem
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 Many solutions give distance per minute.  Other than carefully observing when done, its useful to get some estimates to as how long etching takes.  A couple of techniques: Many solutions give distance per minute.  Other than carefully observing when done, its useful to get some estimates to as how long etching takes.  A couple of techniques:
   * Focus on different layers and measure how much focus knobs had to be turned   * Focus on different layers and measure how much focus knobs had to be turned
-  * Use thin film interference colors: http://www.idea2ic.com/LM13600/SiO2_Color_Chart.pd+  * Use thin film interference colors: https://web.archive.org/web/20170324225827/http://www.idea2ic.com/LM13600/SiO2_Color_Chart.pdf
  
  
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     * Adding HCl may reduce insoluble oxide bi-products     * Adding HCl may reduce insoluble oxide bi-products
  
-===== Pitting =====+==== Pitting ====
  
 A common issue seems to be pitting if left in too long. As BOE itself can't etch silicon, it must be an additive. Some evidence suggests this is caused by not cleaning upper (ie metal) layers away. Possibly due to atmospheric oxygen. This also causes issues for staining and similar processes. A common issue seems to be pitting if left in too long. As BOE itself can't etch silicon, it must be an additive. Some evidence suggests this is caused by not cleaning upper (ie metal) layers away. Possibly due to atmospheric oxygen. This also causes issues for staining and similar processes.
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 {{mcmaster:delayer:wet:gp_overetch:dies.jpg?300}} {{mcmaster:delayer:wet:gp_overetch:dies.jpg?300}}
 +
 Above: left 40 min etch, right 40 hour etch 130F forced air w/ BOE Above: left 40 min etch, right 40 hour etch 130F forced air w/ BOE
  
 {{mcmaster:delayer:wet:gp_overetch:angle1.jpg?300}} {{mcmaster:delayer:wet:gp_overetch:angle1.jpg?300}}
 +
 Above: die at angle, left side lower than right. Right side shows deep pits in focus even though its higher than surface visible at left Above: die at angle, left side lower than right. Right side shows deep pits in focus even though its higher than surface visible at left
  
 {{mcmaster:delayer:wet:gp_overetch:s2-dlyr1_01.jpg?300}} {{mcmaster:delayer:wet:gp_overetch:s2-dlyr1_01.jpg?300}}
 {{mcmaster:delayer:wet:gp_overetch:s2-dlyr1_02.jpg?300}} {{mcmaster:delayer:wet:gp_overetch:s2-dlyr1_02.jpg?300}}
 +
 Above: deep staining shows doping much higher than substate now as evidenced by significant focus difference Above: deep staining shows doping much higher than substate now as evidenced by significant focus difference
  
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   * 1 mL 40% HF   * 1 mL 40% HF
   * 20-25 @ room temp   * 20-25 @ room temp
 +
 +Alternate:
 +  * 1 mL Whink
 +  * 10 mL 70% HNO3
  
 Notes: Notes:
-  * I haven't used this solution yet+  * 2023-07-23: did a good job near top metal when the other solution wasn't working 
  
 ====== References ======  ====== References ====== 
delayer/wet.1516513636.txt.gz · Last modified: 2018/01/21 05:47 by mcmaster