Specific Process Knowledge/Etch/III-V RIE/III V RIE ETCHES

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CHF3/O2 etch

A plasma with a gas mixture of CHF3 and O2 is used to etch SiO2 and Si3N4 dielectricas; flour radicals are responsible for etching the dielectrica while oxygen removes the polymer that is formed during the etch. The polymer deposition rate and SiO2 etch rate are very sensitive to the flow ratio of CHF3 and O2 . The current processes have been optimized from this point of view.

There are 3 standard programs:


CHF3/O2 etch rates, nm/min
Process Name Process parameters SiO2 Si3N4 AZ5206 ZEP520A Negative DUV: UVN 2030-0.5 Comments/links
SiO2_602
  • CHF3-flow: 16 sccm,
  • O2-flow: 2 sccm,
  • Power = 60 W,
  • Vbias = 325 V,
  • Process pressure = 100 mTorr
 30{(1)}   29{(2)} 36{(3)}    
High selectivity to resist
  • CHF3-flow: 17 sccm,
  • O2-flow: 0 sccm,
  • Power = 150 W,
  • Vbias = ? V,
  • Process pressure = 150 mTorr
 85       10.6 dec2019/jan2020 by Qugig and bghe @nanolab
Lower etch rate, medium selectivity to resist
  • CHF3-flow: 17 sccm,
  • O2-flow: 0 sccm,
  • Power = 100 W,
  • Vbias = ? V,
  • Process pressure = 20 mTorr
 49-62 (depending on conditioning)     ~12   Images and reproducibility dec2019/jan2020 by Qugig and bghe @nanolab
Si3N4Ti
  • CHF3-flow: 16 sccm,
  • O2-flow: 2 sccm,
  • Power = 23? W,
  • Vbias = ? V,
  • Process pressure = ? mTorr
   38        

(1) Measured with laser reflectometry 106 (?) nm on G360 fully etched after 3:30: 05-10-11 (2) From Dektak measurement on G360 2005-10-11 (3) From Dektak measurement on D002 (I & II) 2005-10-12. D002 is a pure InP-wafer. (4) Etch rate measured on 140nm wide holes

CH4/H2 etch

This plasma etch is used for etch of InP and InGaAs(P).

In order to ensure unchanged etching conditions during etch, the chamber needs to be primed before using this etch. There are 2 priming programs, clecond and precond. Clecond also cleans the chamber with Oxygen before priming it.

There are 2 standard etch programs for etching InP, InGaAs and InGaAsP: InPstd is for InP-etch while InGaAs1 is for InGaAs- and InGaAsP-etch.

The etch-rates for the CH4 / H2 etch depends highly on the total etching area and on the size of the structrures that are etched, eg ridges or small holes. All rates are given for a total etch area of 2 inches and for etching of ridges, if not otherwise commented. Dektak has been used for the measurement if nothing else is mentioned.


CH4/H2 etch rates, nm/min
Process Name Process parameters InP InGaAs GaAs AlAs SiO2
InPstd
  • CH4-flow: 8.4 sccm,
  • H2-flow: 42 sccm,
  • Power = 60 W,
  • Vbias = 450 V,
  • Process pressure = 80 mTorr,
  • Base pressure = 0.01 mTorr
 29 9     1
InGaAs1
  • CH4-flow: 8.4 sccm,
  • H2-flow: 42 sccm,
  • Power = 60 W,
  • Vbias = 450 V,
  • Process pressure = 80 mTorr,
  • Base pressure = 0.01 mTorr
 29 9      

BCB polymer and Resist etch

The BCB-etch is mainly a O2 etch but a small amount of CHF3 is added to remove Si. There are 3 standard processes: BCB_LP and BCB30LP are low pressure (anisotropic) medium power etches for planarization of BCB, while BCB100W is a high power etch to totally remove thick layers of BCB.

Other resists (ZEP520A, AZ-resists) can be etched by a O2 etch. The standard program is called ASH?m, where the process time is optional.

O2/CHF3 etch rates, nm/min
Process Name Process parameters BCB SiO2 AZ5214
BCB_LP
  • CHF3-flow: 3 sccm,
  • O2-flow: 12 sccm,
  • Power = 30 W,
  • Vbias = 220 V,
  • Process pressure = 10 mTorr
 70 +/- ? 6 +/- ?  
BCB30LP
  • CHF3-flow: 6 sccm,
  • O2-flow: 24 sccm,
  • Power = 30 W,
  • Process pressure = 10 mTorr
 127    
BCB100W
  • CHF3-flow: 10 sccm,
  • O2-flow: 42 sccm,
  • Power = 100 W,
  • Vbias = ~540 V,
  • Process pressure = 100 mTorr
 880   815


O2/ etch rates, nm/min
Process Name Process parameters BCB ZEP520A AZ5214 SiO2
ASH?m
  • O2-flow: 50 sccm,
  • Power = 20 W,
  • Vbias = ~170 V,
  • Process pressure = 150 mTorr
 ? 98 70 6 +/- ?

Chamber Cleaning

Cleaning of the chamber is very important to achieve reproducible etch results. After every etch the chamber should be cleaned. For most CHF3/O2 etch programs a simple clean procedure is sufficient. When BCB has been etched one must use cleanbcb, where CHF3 is added. If CH4 is used in the process (all programs etching III-V compounds) a vlclean procedure is necessary.


Cleaning programs
Process Name O2-flow (sccm) Pressure (mTorr) Power (W) Vbias (V) Time (min)
clean 50       10
Lclean 50       20
vlclean 50       30
cleanbcb 50 100 100   10
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