Specific Process Knowledge/Etch/Etching of SU-8: Difference between revisions

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SU-8 can be etched by a oxygen plasma with a small amount of SF6 to remove the antimony present from the photo initiator.
<!--Checked for updates on 30/7-2018 - ok/jmli -->
<!--Page reviewed by jmli 9/8-2022  -->
 
==Etching of SU-8==
SU-8 can be etched by a oxygen plasma with a small amount of SF<sub>6</sub> to remove the antimony present from the photo initiator. Etching of SU-8 has been developed on the ASE and was tested as a mask less reduction of patterns defined by photo lithography. Two processes are available, a high and a low anisotropic etch for use as etching or thinning of structures.
 
* High anisotropic etch: etch rate ~400nm/min, anisotropy ~0.8
* Low anisotropic etch: etch rate ~170nm/min, anisotropy ~0.3
 
==Recipes in ASE==
===SU8aniso===
The anisotropic SU8aniso etch was design to etch structures in SU-8 with a low roughness of the etched surface, however it has not been tested with any mask material. For a polymeric mask a low selectivity is expected. The etch rate was measured to around 400 nm/min, but will depend on wafer coverage. The surface layer concentration of antimony (Sb) after etch is expected to be below 2%.
 
{| border="2" cellpadding="2" cellspacing="1" style="text-align:center;"
|+ '''SU8aniso and SU8iso etches''' by khara@nanolab
|-
! Parameter
! SU8aniso etch
! SU8iso etch
|-
! O<sub>2</sub> (sccm)
| 99
| 99
|-
! SF<sub>6</sub> (sccm)
| 17
| 14
|-
! Pressure (mTorr)
| 40
| 20
|-
! Coil power (W)
| 800
| 800
|-
! Platen power (W)
| 30
| 0
|-
! Temperature (<sup>o</sup>C)
| 30
| 10
|-
! Etch rate (nm/min)
| ~400
| ~170
|-
!anisotropy
| ~0.8
| ~0.3
|-
!Sb in surface layer (%)
| <2
| <2.75
|}
 
===SU8iso===
The SU8iso etch was developed for thinning of lithography defined structures to gain higher aspect ratio or thinner structures than possible with photo lithography.
 
==Roughness and antimony effects in SU-8 etching==
 
{| border="1" cellspacing="1" cellpadding="2"  align="left"
! SU-8 lines by lithography
! Oxygen etch
! SU8aniso
! SU8iso
|-
|[[Image:SU8-noetch Q13.jpg|200x200px]]
|[[Image:SU8-oxygen-etch_Q12.jpg|200x200px]]
|[[Image:SU8-SU8aniso_R15.jpg|200x200px]]
|[[Image:SU8-SU8iso_R13.jpg|200x200px]]
|-
|No etching
|Etch
*O<sub>2</sub> flow [sccm]:99
*SF<sub>6</sub> flow [sccm]:0
*Pressure [mTorr]:20
*Coil power [W]:800
*Platen power [W]:30
*Temperature [°C]:10
|Etch
*O<sub>2</sub> flow [sccm]:99
*SF<sub>6</sub> flow [sccm]:17
*Pressure [mTorr]:40
*Coil power [W]:800
*Platen power [W]:30
*Temperature [°C]:30
|Etch
*O<sub>2</sub> flow [sccm]:99
*SF<sub>6</sub> flow [sccm]:14
*Pressure [mTorr]:20
*Coil power [W]:800
*Platen power [W]:0
*Temperature [°C]:10
|}

Latest revision as of 10:09, 9 August 2022


Etching of SU-8

SU-8 can be etched by a oxygen plasma with a small amount of SF6 to remove the antimony present from the photo initiator. Etching of SU-8 has been developed on the ASE and was tested as a mask less reduction of patterns defined by photo lithography. Two processes are available, a high and a low anisotropic etch for use as etching or thinning of structures.

  • High anisotropic etch: etch rate ~400nm/min, anisotropy ~0.8
  • Low anisotropic etch: etch rate ~170nm/min, anisotropy ~0.3

Recipes in ASE

SU8aniso

The anisotropic SU8aniso etch was design to etch structures in SU-8 with a low roughness of the etched surface, however it has not been tested with any mask material. For a polymeric mask a low selectivity is expected. The etch rate was measured to around 400 nm/min, but will depend on wafer coverage. The surface layer concentration of antimony (Sb) after etch is expected to be below 2%.

SU8aniso and SU8iso etches by khara@nanolab
Parameter SU8aniso etch SU8iso etch
O2 (sccm) 99 99
SF6 (sccm) 17 14
Pressure (mTorr) 40 20
Coil power (W) 800 800
Platen power (W) 30 0
Temperature (oC) 30 10
Etch rate (nm/min) ~400 ~170
anisotropy ~0.8 ~0.3
Sb in surface layer (%) <2 <2.75

SU8iso

The SU8iso etch was developed for thinning of lithography defined structures to gain higher aspect ratio or thinner structures than possible with photo lithography.

Roughness and antimony effects in SU-8 etching

SU-8 lines by lithography Oxygen etch SU8aniso SU8iso
No etching Etch
  • O2 flow [sccm]:99
  • SF6 flow [sccm]:0
  • Pressure [mTorr]:20
  • Coil power [W]:800
  • Platen power [W]:30
  • Temperature [°C]:10
 Etch
  • O2 flow [sccm]:99
  • SF6 flow [sccm]:17
  • Pressure [mTorr]:40
  • Coil power [W]:800
  • Platen power [W]:30
  • Temperature [°C]:30
 Etch
  • O2 flow [sccm]:99
  • SF6 flow [sccm]:14
  • Pressure [mTorr]:20
  • Coil power [W]:800
  • Platen power [W]:0
  • Temperature [°C]:10
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