Patent ID: 7524683

Claim:
A method of monitoring trends in semiconductor processes, the method comprising: assigning lot values to each of a set of wafer lots prior to performing semiconductor processes on the set of wafer lots, wherein the lot values have an increasing sequential order corresponding to an order in which the set of wafer lots are started in a beginning of the semiconductor processes; after at least some of the semiconductor processes, testing at least some of the wafer lots to generate a set of test data; and calculating a degree of scrambling for the set of wafer lots already tested, the calculating of the degree of scrambling comprising by subtracting a lot value from a largest lot value in the first data set; after a current wafer lot of the set of wafer lots is tested, calculating a current scrambling value by subtracting the lot value of the current wafer lot from a maximum lot value of the lot values assigned for the set of wafer lots to yield the current scrambling value; storing the current scrambling value into a set of scrambling values for the set of wafer lots, wherein the lot values include an average of a set of parameter values selected from the group consisting of moving average, and exponential weighted moving average; and determining a current adjusted maximum scrambling value by multiplying a selected multiplier value with a current maximum scrambling value of the set of scrambling values for a selected number of wafer lots.