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| ==Comparison of wet Silicon Nitride etch and RIE etch for etching of Silicon Nitride==
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| {| border="2" cellspacing="0" cellpadding="4" align="center"
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| !
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| ! Wet Silicon Nitride etch
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| ! Buffered HF (BHF)
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| ! RIE
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| |- valign="top"
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| ! General description
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| *Isotropic etch
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| *Well suited for removing all nitride on a wafer surface (nitride strip) without a mask. High selectivity Si<sub>3</sub>N<sub>4</sub>/Si (>100) and Si<sub>3</sub>N<sub>4</sub>/SiO<sub>2</sub> (>20) @ 180 C.
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| *Isotropic etch
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| *Well suited for removing all PECVD nitride on a wafer surface (nitride strip) without a mask. Etches LPCVD nitride very slowly
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| *Anisotropic etch: vertical sidewalls
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| |- valign="top"
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| !Possible masking materials
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| *Silicon Oxide
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| *PolySilicon
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| *Photoresist
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| *PolySilicon
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| *Blue film
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| *Photoresist
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| *Silicon Oxide
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| *Aluminium
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| *Chromium (ONLY RIE2!)
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| *Other metals if they cover less than 5% of the wafer area (ONLY RIE2!)
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| |- valign="top"
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| !Etch rate
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| *Si<sub>3</sub>N<sub>4</sub> @ 180 <sup>o</sup>C: ~84 Å/min
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| *Si<sub>3</sub>N<sub>4</sub> @ 160 <sup>o</sup>C: ~60 Å/min
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| *PECVD nitride: ~400-1000 Å/min
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| *Typically 40-50 nm/min can be increased or decreased by using other recipe parameters.
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| |- valign="top"
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| !Batch size
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| *1-25 wafers at a time
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| *1-25 wafers at a time
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| *1 wafer at a time
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| |- valign="top"
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| !Size of substrate
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| *4" wafers
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| *4" wafers
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| *4" wafers or smaller pieces
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| |- valign="top"
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| !Allowed materials
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| *Silicon
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| *Silicon Oxide
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| *Silicon Nitride
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| *Silicon Oxynitride
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| *Silicon
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| *Silicon Oxide
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| *Silicon Nitride
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| *Silicon Oxynitride
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| *Photoresist
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| *Blue film
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| *Silicon
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| *Silicon Oxide
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| *Silicon Nitride
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| *Silicon Oxynitride
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| *Photoresist
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| *E-beam resist
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| *Aluminium
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| *Chromium (ONLY RIE2!)
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| *Other metals if they cover less than 5% of the wafer area (ONLY RIE2!)
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| |-
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| |}
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