Question

In semiconductor manufacturing, Deposition is a batch process that coats materials on silicon wafers in a heated oven-like facility. Intal Corp. has a semiconductor wafer fabrication factory that has one Deposition facility that can take up to 50 wafers in one batch. The setup time for heating the facility to the appropriate temperature is 1 hour. It then takes another 2 hours to complete the Deposition for one batch of wafers. The factory runs a push production and wafers depart from the previous process and arrive at the Deposition facility with an average arrival rate of 10.1 wafers per hour. What is the minimum batch size at Deposition in order to have a stable process without a continually growing job queue?

(This is similar to one of the examples in the batching lecture but with a simpler (simultaneous batch) setting.)

	10.1*1/(1–1/10.1) = 11.2, so the minimum batch size is 11
	10.1*(1+2) = 30.3, so the minimum batch size is 30

	10.1*(1+2) = 30.3, so the minimum batch size is 31
	10.1*1/(1–1/10.1) = 11.2, so the minimum batch size is 12

the minimum batch size is 50, the maximum that the Deposition facility can take.

Answer 1

Current on hand inventory = 1308 units

Withdrawal quantity = 95 units

Net quantity post withdrawal = 1308 – 95 = 1213

Since net quantity post withdrawal ( i.e. 1213 ) > Reorder point 1150, IT IS NOT YET TIME TO REORDER

In order to achieve a stable process ,

it is essential that Flow rate ( wafers / hour ) from previous process = Deposition rate ( Wafers/hour ) .

There will be inventory built up if flow rate from previous process > Deposition rate

Given flow rate from previous process = 10.1 wafers/ hour

Total time for deposition process = Heating time + deposition time = 1 hour + 2 hours = 3 hours

Therefore , in order to achieve a stable process, deposition process also must achieve a rate of 10.1 / hour . Thus batch size of the deposition process = 10.1 hour x 3 hours = 30.3 hours

ANSWER : B) 10.1( 1 + 2 ) = 30.3 , SO THE MINIMUM BATCH SIZE IS 30