Specific Process Knowledge/Etch/III-V ICP/InP-InGaAsP-InGaAs

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InP etch with HBr chemistry (2019)

Work done by Aurimas Sakanas @Fotonik.dtu 2019. This work was done to obtain very low surface roughness.

Recipe name ?
HBr flow 10 sccm
CH4 flow 5 sccm
Ar flow 2 sccm
Platen power 50 W
Coil power 600 W
Pressure 5 mTorr
Platen chiller temperature 180 oC
Comment Sample crystal bonded (Crystalbond 509, clear color) to Si carrier
Results
Etch rate

250-350 nm/min (2" wafer)
350-450 nm/min (quarter of a 2" wafer)

Sidewall angle

85-87o (bottom)
93-95o (top)
Concave profile

Selectivity (InP:HSQ) 15:1 (2"), 20:1
Other tests Comparing this recipe with the Cl2/H2 recipe, click here: Media:HBr vs Cl2 InP etch comparison Aurimas.pptx (By Aurimas Sakana @photonic (nov 2019))
  • 200 nm wide line structure, tetch=25 s
    200 nm wide line structure, tetch=25 s
  • 700 nm wide line structure, tetch=25 s
    700 nm wide line structure, tetch=25 s
  • 200 nm wide line structure, tetch=2 min
    200 nm wide line structure, tetch=2 min
  • 400 nm wide line structure, tetch=2 min
    400 nm wide line structure, tetch=2 min
  • 1 µm wide line structure, tetch=2 min
    1 µm wide line structure, tetch=2 min
  • Two 1 µm wide line structure, 300 nm gap, tetch=25 s
    Two 1 µm wide line structure, 300 nm gap, tetch=25 s
  • Two 1 µm wide line structure, 300 nm gap, tetch=2 min
    Two 1 µm wide line structure, 300 nm gap, tetch=2 min
  • Two 1 µm wide line structure, 500 nm gap, tetch=2 min
    Two 1 µm wide line structure, 500 nm gap, tetch=2 min
  • Two 1 µm wide line structure, 1 µm gap, tetch=2 min
    Two 1 µm wide line structure, 1 µm gap, tetch=2 min

InP etch with Cl2/H2 and a Si carrier wafer (2019)

Work done by Berit Herstrøm @Nanolab spring 2019

Recipe name ?
Cl2 flow 6.6 sccm
H2 flow 5.4 sccm
Process time 6 min
Platen power 150 W
Coil power 800 W
Pressure 0.5 mTorr (strike pressure 10s@10mTorr)
Platen chiller temperature 180 oC
Comment Sample placed on a Si carrier
Results
Etch rate

925 nm/min (small piece)

Sidewall angle

90o (on this sample)
If you get a small tapered profile try lowering the platen power (to e.g. 100W), this will also decrease the etch rate

Selectivity (InP:SiO2 (PECVD 500nm) approx.17:1
Other tests made Comparing of this Cl2/H2 recipe with HBr recipe on e-beamed structures:Media:HBr vs Cl2 InP etch comparison Aurimas.pptx (By Aurimas Sakana @photonic (nov 2019))

InP etch with Cl2/CH4/Ar 2013

Work done by Matthew Haines in 2013

InP/InGaAsP/InGaAs etch 2011

Unselective etch for large sized features and small aspect ratios by David Larsson, DTU Photonics, 2011

Recipe InP Etch 1/InP Precond 1
Cl2 flow 20 sccm
N2 flow 40 sccm
Ar flow 10 sccm
Platen power 100 W
Coil power 500 W
Pressure 2 mTorr
Platen chiller temperature 180 oC
Comment Use SiO2 carrier (not Si) (Kabi/Bghe June 2018)


Results (InP Etch 1)
Etch rate 500-600 nm/min
Sidewall angle 86-87 o
Selectivity (InP:SiO2, InP:HSQ) 50:1
  • Result of InP etching. David Larsson, DTU Photonics, 2011

InP etching June 2018

Done by Kabi and Bghe @danchip

Sample pattern before etching

  • Oxide mask before etching.
  • Top view of the SiO2 mask before etching
    Top view of the SiO2 mask before etching
  • Top view of the SiO2 mask before etching
    Top view of the SiO2 mask before etching

Etching of an InP piece on Si carrier

InP piece patterned with SiO2. The piece was etched on top of a Si wafer without bonding. The recipe "InP etch" was used. The roughness looks high in the bottom of the etched areas, especially in the large open areas.

  • Result of InP etching.
  • low roughness in narrow trenched
    low roughness in narrow trenched
  • low roughness in narrow trenched
    low roughness in narrow trenched
  • A little higher roughnedd is larger trences
    A little higher roughnedd is larger trences
  • Much larger roughness in open areas
    Much larger roughness in open areas
  • Zoom in on the large roughness
    Zoom in on the large roughness
  • closed look at the large roughness in the open areas.
    closed look at the large roughness in the open areas.

Etching of an InP piece on SiO2 carrier

InP piece patterned with SiO2. The piece was etched on top of a Si wafer coated with SiO2 without bonding. The recipe "InP etch" was used. The roughness looks low in the bottom of the etched areas, even in the large open areas.

  • Result of InP etching.
  • Top view: oxide is gone on the narrow lines, low roughness in the trenches.
    Top view: oxide is gone on the narrow lines, low roughness in the trenches.
  • Top view: low roughness in the trenches.
    Top view: low roughness in the trenches.
  • 30 dg view: low roughness in the trenches
    30 dg view: low roughness in the trenches
  • 30 dg view: low roughness in the trenches
    30 dg view: low roughness in the trenches
  • Top view: low roughness in trench and in the large area
    Top view: low roughness in trench and in the large area


Changing the Cl2/N2 ratio

  • Result of changing the Cl2/N2 ratio.
  • Sample S0: Top view of the oxide mask before etching. It is the TRAVKA50 mask, but it is clear that the CD reduction is about the 1-1.5 µm of the lines.
    Sample S0: Top view of the oxide mask before etching. It is the TRAVKA50 mask, but it is clear that the CD reduction is about the 1-1.5 µm of the lines.
  • File:None
  • Sample S4: Profile view. The recipe InP etch has been used. The sample has been run on a SiO2 carrier wafer. There is not much CD change compared to the oxide mask before the etch. It seems like the SiO2 mask is gone and the sidewall angle from the mask has been transferred into the sample. The sidewall profile is quit vertical in the lower part. Etch time 15 min Etch depth in large open areas: 9.19µm
    Sample S4: Profile view. The recipe InP etch has been used.
    The sample has been run on a SiO2 carrier wafer.
    There is not much CD change compared to the oxide mask before the etch.
    It seems like the SiO2 mask is gone and the sidewall angle from the mask has been transferred into the sample.
    The sidewall profile is quit vertical in the lower part.
    Etch time 15 min
    Etch depth in large open areas: 9.19µm
  • Sample S5: Profile view. The recipe InP etch has been used but with modified Cl2 and N2 flows: N2=30 sccm Cl2=30 sccm. The sample has been run on a SiO2 carrier wafer. There is not much CD change compared to the oxide mask before the etch. It seems like the SiO2 mask is gone. The sidewall profile is overcutting probably due to too little passivation. Etch time 10 min Etch depth in large open areas: 11.82µm
    Sample S5: Profile view. The recipe InP etch has been used but with modified Cl2 and N2 flows: N2=30 sccm Cl2=30 sccm.
    The sample has been run on a SiO2 carrier wafer.
    There is not much CD change compared to the oxide mask before the etch.
    It seems like the SiO2 mask is gone.
    The sidewall profile is overcutting probably due to too little passivation.
    Etch time 10 min
    Etch depth in large open areas: 11.82µm
  • Sample S4: The sidewall roughness on the sample S4 is quit high
    Sample S4: The sidewall roughness on the sample S4 is quit high
  • Sample S5: The sidewall roughness on the sample S5 is quit low.
    Sample S5: The sidewall roughness on the sample S5 is quit low.
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