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Using photoresist

Photoresist can be used to attach pieces to a carrier wafer. The commonly available resist in the lab may be used, 3612, SPR22-3 or -7. PMMA may also be used but it is described in another procedure page.

Pros and Cons 

 

Pros

  • Easily available
  • Easy to apply
  • Can be used in 'clean' systems

 

Cons

  • Can be time consuming to separate wafers
  • Poor thermal transfer
  • Cannot be used about 120C
  • May not be used in the HD PECVD system.

 

 Using Photoresist

 

This procedure has been used for through wafer etching at the stsetch for some time.  It may also be useful in other etchers provided the etching process doesn't get hot.

 

Note: Good resist adhesion is dependent on a dry surface. If the wafers haven't recently come out of a high temperature furnace (out for more than 1 hour), they should get a singe at 150C for 30 minutes.

  1. Run the wafers through the yes oven..
  2. Coat a backing (support) wafer with 1.65um 3612 resist.
  3. Place your device wafer on top of the support wafer and align the flats as best you can.
  4. Place the wafers on a hotplate (set at 105C) and place foil over the wafer to protect the surface. Put the weight on top of the foil (the weights are near the hotplate).
  5. Bake on the hotplate for 1 hour.
  6. Coat your wafer with the SVGCOAT using program 1 on the prime station and program for the desired thickness on the coat station ( for example Program 4 for 7um). You may choose not to use the edge bead removal steps.
  7. Expose, develop and postbake.
  8. Do an additional post bake in the 90C (45-60 mins) or 110C (30 mins) to further harden the resist.

 

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