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Experimental Plan

Experimental plan for STSetch2 characterization, by Srikant Vaithilingam (Coral login: srikantv).

Khuri-Yakub Group, Stanford University

Experimental plan for STS2 characterization

Target: Test whether STS recipes are working as expected. We will focus on deeper etches of ~250 micron. We will check if SPR 220-7 photoresist can be used in the machine. We will document etch profile, undercut, resist selectivity using Nanospec and uniformity across wafer. We plan to test two recipes from the STS defaults – High-Aspect Ratio recipe and General MEMS recipe.

Timeline: Finish by end of Jan 2010

Test tool: STS2

Characterization tools:
1. Resist Thickness – Nanospec
2. Profile – SEM
3. Undercut - SEM
4. Uniformity across wafer - SEM

Recipe Parameter tuning:
1. Necessary only if standard recipe provided by STS does not do the job
      a. General MEMS Recipe
                    450 SF6 + 45 O2 (8.5s)
                    200 C4F8 (3s)
                    MANUAL APC to give 35-40mT, 12mTd
                    2200We/1500Wd coil
                   40We/20Wd platen [13.56MHz]
                   EM1 2A, 2.5s delay (etch only)
                   10T He, 10°C platen temperature
                   96mm electrode spacers
      b. High Aspect Ratio Recipe
                    200 SF6 +20 O2 (4s)
                    200 C4F8 (3s)
                    AUTO pressure 26mTe/12mTd
                    Coil 2kWe/1.2kWd
                    Platen 85We / 0Wd [13.56MHz]
                    EM1: 2s delay, 2.5A (etch only)
                    10T He, 10°C platen
                    96mm electrode spacers

Test Mask:

1. Patterns of circles, donuts and trenches with a range of diameters and trench widths
2. Repeating patterns emanate from the center of wafer so that we can check for uniformity across the wafer

General experimental procedure:
1. Coat SPR 220-7 resist according to datasheet and an additional hard bake on hotplate
2. Expose using our test mask.
3. Take microscope pictures
4. Measure resist thickness on Nanospec
5. Etch on STS2 for X minutes using two different standard recipes provided by STS (mentioned above)
6. Take microscope pictures
7. Measure resist thickness on Nanospec
8. Cleave/dice wafer
9. SEM
a. Profile
b. Undercut
c. Uniformity across wafer

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