Mathies:Nitride: Difference between revisions

  1. Use the 6" anodic bonding fixture (stored on ksbonder)

  2. Use the 4" Si fusion chuck (not the vacuum one)

  3. Use Program [2] (Si fusion, Load:slide, Unload:fixture)

          * Basically, ksba6 doesn't know the difference between the 2 fixtures, but we want the anodic bonding fixture so that we can clamp the aligned wafers rather than dumping them on the chuck again.

  4. Load top (Si) wafer and capture an image of the back side.

  5. Load bottom (glass) wafer and align to image of top wafer

  6. When aligned, press "Clamp"

  7. Remove the fixture and use a binder clip to clamp the wafers in place.

  8. Remove the spacer flags carefully.

  9. Undo the fixture clamps (but leave the binder clip in place)

  10. You can flip the wafer stack over if you are doing anodic bonding (b/c it needs the opposite orientation).

  11. If you are doing Si-Si bonding where you can't see the bond quality you need to use the IR microscope...

  1. Turn on the white bucket lamp located underneath the camera. The switch is a rotary switch located on the power cord near the lamp end. The lamp is just a simple light bulb. If it burns out, you can ask the Microlab office for a new one, or, if it's the weekend and you're desperate, you can just go to ACE hardware. Flood lamps work better because they have a flatter intensity profile, but any lamp will do. You might want to check the wattage, though.

  2. On the computer's Windows desktop, open XCAP for windows

  3. After agreeing to some conditions (which sell your firstborn children to Mr. XCAP), you will see a window that has a big square for the video/snapshots, and a diagram of the back of a PCI video input card on the left side of the screen. In this EPIX® PIXCI® SV: Capture & Adjust window, click on the UPPER middle circle so that it is highlighted in red. This is the video input port for the IR Camera (the lower circle is for Reichert). Then select the button for Live. The window EPIX® PIXCI®: View #1 should now be showing live video of the IR camera.

  4. If you don't have anything between the lamp and the camera, you'll probably just see a white screen because the intensity is too high (the camera is sensitive to visible light, too). Place your sample on the ring stand and see if you can see your features. You shouldn't need to adjust the focus, as the ring stand has been adjusted to the focal length of the camera.

  5. If the intensity is still too high (white screen), there are usually one or two plain silicon wafers sitting next to the lamp. Put these directly on top of the lamp's top frame. These will attenuate the visible and IR light so that you can get better contrast/less saturation with the camera. If it is too dark, move the wafers so that they only partically cover the top of the lamp.

  6. Sometimes, you'll see some weird white cloudy spots in your picture which don't really matter but look bad if you're trying to use a picture for a talk/publication. These white spots are glare from metal nearby (like the post of the adjustable camera mount). Usually a strategically placed technicloth can get rid of this glare.

  7. When you are ready to take a picture, click the Unlive radio button to freeze the image. If you want to refresh the image, press Snap in Unlive mode.

  8. Save the image with File -- Image Save. Create a directory for yourself and delete pictures when you have transferred them to external disk or server.

  9. More info can be found in the Reichert chaper of the Microlab manuals.

  1.  Use programs "o" or "p". P doesn't have the over etch.

  2. To prevent photoresist burning:

          * HARD BAKE YOUR WAFERS!

            30 min in vwroven, or use uvbake (for Si only).

          * use 700 W instead of 850 W power. etch rate of oxide ~ 500 nm/min. nitride is a little less, but close.

          * don't let the temperature get over 14C. don't etch for much over 1 minute at a time. Wait for 1 minute in between etch steps.

          * use g-line resist + g-line uvbake program for best results.

    *  HF programs:

      VEE6 (deep etch, preferred, ~3 um/min etch rate)

      AARON6A (deep etch, OK)

      HEXA250 (lots of undercutting, not so great)

      LIPPMAN1B (smooth edges, slow etch)

    * Low frequency programs:

      Use to prevent "footing" (widening of channels when you hit the bottom oxide or buried SOI layer). Basically, the platen power will cycle off and on, allowing the charged ions that build up near the insulating layer to dissipate and preventing distortion of electric fields that screw up anisotropic etching.

    * Use 20 ms period, 25% duty cycle. The VEE9 LF program works very well, with ~ 2 um/min etch rate for big channels, ~1.67 um/min for 40 um channels. Other programs:

      ROLF1B (not so great)

      Lipman1C (~1.4 um/min)

      Anita1B (lots of grass?)

    * For best results, run the COND3 recipe on a plain Si wafer before etching (35 minutes)

    * Use a 1 um oxide (tystar12 LTO) hardmask for deep etches and nice lines.

    * Etch for 10 s in Lam 2 (program P) to remove native oxide before STS. This increases uniformity and reduces grass.

    * For the best through etching, I use SPR-220 photoresist (10 um) and Cool Grease for handle wafer bonding. Here are my parameters.

          o SPR220-7

              1. Spin SPR220 on Spinner1 (much better than SVG coat)

                  10s ramp -- 500 RPM -- hold 10s -- 10s ramp -- 1.8 KRPM -- hold 30s

              2. Soft bake 5 min, 115C hot plate, NO FOIL!

              3. Expose 280 mJ/cm on ksaligner, soft contact mode

              4. NO post-expose bake! It just induces cracking,etc.

              5. Wait 30 min before developing for 1.5 min in LDD26W.

              6. Hard Bake 15 min on 95C hot plate

              7. Etch 1 um oxide hard mask on Lam2 (2 min, 700W)

          o Cool Grease handle wafer bonding

              1. Put a piece of foil on a 65C hot plate.

              2. Place handle wafer (1 um oxide) on hot plate.

              3. Spread AI Technologies Cool Grease on handle wafer with a glass slide. (cover completely)

              4. Smush your photoresist-covered wafer on dummy wafer while on hotplate. Make sure to align the flats. Use the big aluminum cooling block to smuch them evenly (use foil on top to protect wafers).

              5. Use poly gloves for everything because the cool grease gets everywhere.

              6. Leave block on wafer stack on hotplate for 5 min.

 

              8. Bake in 60C OVEN for 15 min.