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Manual for SPTS APS (Dielectric Etcher)

SPTS APS SPTS APS

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Attention To be read first:

SPTS APS is an etcher dedicated to dielectrics (SiO2, Si3N4, glass types...). Dielectrics etching in AMS200 is no more CMi standard. AMS200 is now dedicated to Si etching.

Contents: CMI

  1. Introduction
  2. Processes available
  3. Modus Operandi
  4. Photos gallery

I. Introduction CMI

SPTS Advanced Plasma System (APS) module is an ICP-based high density plasma source. This system was optimized for etching dielectrics (e.g. SiO2, SixNy, SiC, Al2O3, glass types...) which are usually difficult to etch using conventional RIE or ICP sources.

Main features of the system are:

  • High density plasma source
  • Wafer voltage biasing independent from the ICP
  • Electrostatic clamping => no EBR required
  • Powerful gas process pumping arrangement
  • Loadlock/chamber transfers for single wafer processing
  • Control software offering fully automated processes
  • End-point detection system (optical spectroscopy)
  • Gases availables:

  • O2 [0 - 100 sccm].
  • Ar [0 - 100 sccm].
  • CHF3 [0 - 100 sccm].
  • He [0 - 500 sccm].
  • C4F8 [0 - 100 sccm].
  • SF6 [0 - 100 sccm] & [0 - 500 sccm].
  • H2 [0 - 50 sccm].
  • II. Processes available CMI

    Materials SH temp (°C) Process name Chemistry Mask material Etch rate (nm/min) Selectivity with Resist EPD
    Si3N4 10 Si3N4 smooth CHF3/SF6 ZEP
    PR
    Si3N4: 160 to 220
    Si: 235
    WetOx: 165
    PR: 70
    2 : 1 Yes
    concening Si3N4 smooth process Note1: SiN etch rate is load-dependent!
    Note2: Silicon isotropic etching !

    SiO2, Si nitride

    10 SiO2 PR 1:1 He/CHF3 PR WetOx: 200
    Si3N4: 200
    SiN LS: 185
    Si: 95
    1.7 : 1 Yes
    SiO2, Si nitride 10 SiO2 PR 2:1 He/C4F8 PR WetOx: 410
    Si3N4: 110
    SiN LS: 95
    Si: 50
    2.8 : 1 Yes
    SiO2, Si nitride 10 SiO2 PR 3:1 He/H2/C4F8 PR
    ZEP / CSAR
    WetOx: 345
    Si3N4: 255
    SiN LS: 190
    Si: 35
    ZEP / CSAR: 130
    4.2 : 1 Yes
    SiO2, Si nitride 10 SiO2 PR 3:1 SOFT He/C4F8 PR WetOx: 295
    Si3N4: 70
    SiN LS: 60
    Si: 35
    3.7 : 1 Yes
    SiO2, Si nitride 10 SiO2 PR 5:1 He/H2/C4F8 PR WetOx: 215
    Si3N4: 255
    SiN LS: 235
    Si: 25
    6.5 : 1 Yes
    Polyimide 10 Pi_vertical O2 PR
    SiO2
    PI (PR) : 1300
    PI (SiO2) : 2300
    ~ 1 : 1 Yes
    Polyimide 10 Pi_tapered O2 PR
    SiO2
    PI (PR) : 800
    PI (SiO2) : 1100
    ~ 1 : 1 Yes
    Fused Silica 20 Fused Silica C4F8/O2 Al 760 12.5 : 1 No
    Pyrex 25 Pyrex C4F8/O2 Al 580 8 : 1 No
    Chamber clean 20 O2 Clean with wafer O2 -- -- -- Yes

    On the SPTS etcher, a process is defined as a sequence of several steps:

    1. Wafer is loaded in, clamped and helium back cooling is switched-on.
    2. Wafer cooling condition is checked by a leak-up-rate (LUR): the chamber is isolated from the pumping system and increase of pressure inside the chamber is recorded. This pressure increase is due to helium leaking in between the chuck and the clamped wafer. To ensure correct cooling of the wafer during etching, LUR should not exceed 80mtorr/min.
    3. Wafer is etched and the End-Point Detection (EPD) system starts automatically. EPD system is used in "monitoring only" mode and therefore it does not control the process chamber. If no action is done by the operator to manually stop the etching, the process will run until the set time has elapsed, even if an end point is detected by the EPD system.
    4. Dechuck step: electrostatic clamping is switched-off and a low power argon plasma runs for few seconds to help removing accumulated charges that may remain. No chuck biasing is applied here to ensure no sample damage by argon ions.
    5. The wafer is unloaded and, if necessary, an automatic cleaning of both the chamber and the chuck starts, stopping automatically unpon end-point detection.
    6. Machine is ready for another run.

    Clearing the PR mask after Si3N4 and SiO2 etch requires both dry and wet treatments:
    1. Start with an oxygen plasma using the Tepla GiGAbatch.
    2. Then do a wet remover treatment using the Ultrafab wetbench.
    3. If necessary, remove final residues with the Tepla GiGAbatch again.

    III. Modus Operandi CMI

    1. System is in idle mode by default: no wafer is loaded, CTC software is open (if not open it), loadlock is under vacuum.
    2. First login in the CTC software: Select the account "other", and enter : 1 (for the account) 1 (for the password).
    3. Select:
      • (a) Recipe,
      • (b) APS1 (hit the cross),
      • (c) Process Module (hit the cross),
      • (d) The process you are interested in (hit the cross),
      • (e) The etching step (SiO2_PR_2:1 in the example)
      • (f) Process parameters are visible, you can only modify the process time in General
      • (g) Save the change (hit Apply on the right)

    4. Select the "Automatic" mode, "Vent" the load lock, and load the wafer on the loading arm.

    5. Select a batch recipe in the predefined batch recipes list.
    6. Click on "Start" icon and check that the batch uses the correct recipe. Then click "Next" and finally "Start". This loads the wafer inside the process module and starts automatically the ecthing sequence detailed previously.
    7. Select the "Manual" mode and click onto "Process (APS1)". Check the LUR test and write-down its value in the follow-up file of SPTS etcher available on the table.
    8. If no action is done by the operator to manually stop the etching, the process will run until the set time has elapsed.
      If the etching has to be stopped before the set time, i.e. after end-point is detected, proceed as follows:
    9. Manual stopping upon EPD control
      Be sure "Manual" control and "Process (APS1)" are active:

      Activate the end-point tab and click "Endpoint":


      The Oxide EPD recipe follows the intensity of the 440nm spectral line which corresponds to SiF (etching by-product).

    10. Then, the system runs the dechuck step, unloads the wafer, vents the loadlock and runs the automatic cleaning of both chamber and chuck (if applicable).

    11. The Oxygen EPD cleaning recipe follows the intensity of the multi-region 685nm to 695nm spectral lines which correspond to COx (cleaning by-products).

    12. Load the next wafer to be etched or if you are done pump the load lock.

    IV. Photos gallery CMI


    Figure 1: Si3N4 etch with Si3N4 smooth.


    Figure 2: SiO2 etch with SiO2 PR 3:1.


    Figure 3: 60min etch of fused silica with aluminum mask.


    Figure 4: 60min etch of pyrex with aluminum mask.


    Figure 5: Polyimide recipes.