A silicon wafer is oxidized to a thickness of 3,000 using dry oxygen and patterned as shown. In region 1, 3,000 of oxide

A silicon wafer is oxidized to a thickness of 3,000 Å using dry oxygen and patterned as shown. In region 1, 3,000 Å of oxide remains, while in region 2, all of the oxide is removed. The wafer is then placed back into the oxidation furnace and heated to 1,000°C in dry oxygen. New oxide will now grow in both regions. Assume the Deal-Grove model is applicable and neglect orientation effects. Rate constants are shown below.

 

(a) How long must the wafer remain in the furnace such that: Oxide thickness in region 2 = 0.5 x (Oxide thickness in region 1) 

 

(b) Suppose all the oxide is removed. What is the magnitude of the height difference, in angstroms, between the regions 1 and 2? 

 

Region 1 Region 2 Si wafer