Sop #11

Title: Vacuum Dehydration Bake

Purpose:  To prepare the surface of the wafer for photoresist 
          application. This operation promotes adhesion of the photoresist 
          by evaporating any moisture present on the surface of the wafer.

NOTE:     A dehydration bake is especially important when delays 
          between substrate preparation (growing oxide, evaporating
          layers, sputtering layers etc.) and resist application
          occur.

Preparation and Precautions:
1.   Oven #1 is dedicated to the dehydration bake. Temperature in this 
     oven should read 200° C± 5° C. 

2.  In case the oven door has been left open prior to use, follow the
    appropriate procedure and allow temperature to stabilize before
    baking wafers.

IMPORTANT: If another temperature setting is desired, refer to the 
           Blue-M Vacuum Oven SOP. 

Procedure With Vacuum:
1.   The oven will be under vacuum. To open the door of the oven, shut 
     off VACUUM valve to isolate the oven from the vacuum source. Open
     VENT valve to bleed air into the oven. Open the oven door when
     the oven is under the atmospheric pressure.

2.   Place wafer face up on one of the shelves in the oven.

3.   To put oven under vacuum: close the door. Close VENT valve to 
     isolate oven from the atmosphere. Turn on the vacuum pump. Open
     VACUUM valve.  The vacuum should start building up as manifested
     on the vacuum gauge.
 
4.   Let the vacuum build up to about 15 inch Hg. Close VACUUM valve,
     isolating the oven.

5.   Bake the wafers for a minimum of 30 minutes.

6.   At the end of the bake, release vacuum and open the oven door as
     step 1.Remove wafers with help of tweezers. Close the oven as 
     steps 3 and 4.

Procedure Without Vacuum:
1.   The oven will be under vacuum. Open the oven door when the oven is 
     under the atmospheric pressure.

2.   Place wafer face up on one of the shelves in the oven.

3.   Close oven door

4.   Bake the wafers for a minimum of 30 minutes.

5.   At the end of the bake, remove wafers with help of tweezers. 
     Close the oven and proceed to the next process or store the wafers 
     in a clean wafer holder.