tailieunhanh - Production Process Characterization_2

Tham khảo tài liệu 'production process characterization_2', kỹ thuật - công nghệ, điện - điện tử phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Controlled Uncontrolled Variation ENGINEERING STATISTICS HANDBOOK home TOOLS a AIDS ISEAECH l ACK next 3. Production Process Characterization . Introduction to Production Process Characterization . Terminology Concepts . Process Variability Controlled Uncontrolled Variation Two trend plots Examples of in control and out of control processes The two figures below are two trend plots from two different oxide growth processes. Thirty wafers were sampled from each process one per day over 30 days. Thickness at the center was measured on each wafer. The x-axis of each graph is the wafer number and the y-axis is the film thickness in angstroms. The first process is an example of a process that is in control with random fluctuation about a process location of approximately 990. The second process is an example of a process that is out of control with a process location trending upward after observation 20. This process exhibits controlled variation. Note the random fluctuation about a constant mean. 1160 HdQ 1060 1H4Ũ 1020 1000 ID BO BBD http div898 handbook ppc section1 1 of 2 5 1 2006 10 17 21 AM Controlled Uncontrolled Variation This process exhibits uncontrolled variation. Note the structure in the variation in the form of a linear trend. 10SO 1060 1040 1020 11 CD 1000 http div898 handbook ppc section1 2 of 2 5 1 2006 10 17 21 AM . Propagating Error ENGINEERING STATISTICS HANDBOOK hW tools raids lỉEÂtCH BACK Nixf 3. Production Process Characterization . Introduction to Production Process Characterization . Terminology Concepts . Propagating Error The variation we see can come from many sources When we estimate the variance at a particular process step this variance is typically not just a result of the current step but rather is an accumulation of variation from previous steps and from measurement error. Therefore an important question that we .