Statistics for Semiconductor Manufacturing Homework 3

Objective

Construct an np control chart using the qcc package in R to confirm process stability and establish control limits for ongoing monitoring.

UCL and LCL Formulas

\[ UCL = np + 3\sqrt{np(1-p)} \]

\[ LCL = np - 3\sqrt{np(1-p)} \] Where:

LCL: lower control limit

UCL: upper control limit

n: sample size

p: the proportion of defective wafers

Control Chart

Results Interpretation

There are no defect count data points that fall outside of the UCL (14.4) or LCL (0); this data shows that the process is operating within control limits. Otherwise, the central mean is 7.2 defective wafers/lot, and the std. dev. of defects is 2.4.