A.7


A.6b Contact Window Etch:

      (1) Etch in buffered HF for 3 minutes, check for complete

           removal of oxide.

      (2) Strip PR and clean up same as A.2b. Front Side Metallization: A.7a In the alloy furnace set at 450 degrees C, 5 minutes in N2;

      15 minutes informing gas, 5 minutes in N2. Gas flow = 800

      cc/minute in all cases.

A.7b  Evaporate 800 nm aluminum over the front surface of the wafe A.7c PR with Metal Mask NBS-4-4AB. Same as A.2a (front side only,

      use silizane).

A.7d   Etch in Al etchant of 20 H3PO4;5H20:IHN heated to 50 degrees

      C until the etching is complete (about 2 minutes). A.7e Rinse in DI water for 10 minutes. A.7f Strip PR in J-l00 and methyl as prescribed in A.2b (3 minute

      in 80 degrees C J-100).

 Back Side Contact:

 A.8a  Dry for 30 minutes in 200-degree C oven. A.8b Spin PR on front side as prescribed in A.2a (no mask).

       Expose to U.V. light for 4 seconds.

 A.8c  Hard bake at 130 degrees C for 30 minutes. A.9d  Dip in 10 percent HF until oxide has been removed from the

       backside of the wafer.

 A.8e Remove PR in J-100 and methyl as prescribed in A.2b (do not

       use cleaning procedure).

 A.8f Scribe the wafer to separate the Hall devices.


A.8


S


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