Industrial Example I Semiconductor Manufacturing Photolithography Can you tell me anything about this data!

Transcription

1 Can you tell me anything about this data! 1

2 In Semiconductor Manufacturing the Photolithography process steps are very critical to ensure proper circuit and device performance. Without good CD (critical dimension: gate widths, contact holes, metal linewidths) control (i.e. least variation), a manufacturer cannot achieve high profit margins and hence stay in business. 2

3 CD control : manufacturer s spend lots of money trying to achieve good CD control. Sources of CD variation are many. Some include: Vendor photoresist and developer chemical batch to batch control Incoming wafer film thickness control Coat equipment control of Thickness and bake temperature Exposure equipment control of dose and focus Post exposure bake temperature and Develop time Measurement equipment repeatability and reproducability 3

4 CD control : Measures of variation types: Intra-part (intra field): within a field on a wafer Intra-part (intra-wafer): Within the wafer or across the wafer. Also can be inter-field. Inter-Part (Inter-wafer): Wafer to wafer within a lot typically Intra-lot (Inter wafer across a single lot) Inter-lot: lot to lot First step We need to find out what the major type of variation is, before we tackle any advanced statistical tests or we risk going off in the wrong direction and wasting time and money!! 4

5 CD control : So what do we do to locate the major type of variation? Take measurements of parts and lots as intra and inter and over time. 5

6 CD control : Intra-wafer: measured all fields across a wafer using 2 measurement features called A and B 6

7 CD control : OK so now what can we do with this data to get maximum amount of information about CD variation? Data ia limited to a single wafer in this case so we can only get information about intra-wafer CD variation. So where do we start? 7

8 CD control : Can ask question : Is there any difference between this A and B feature as measured? 8

9 CD control : Is there any difference between this A and B feature as measured? Descriptive Statistics ( from Excel) A FORK B FORK Mean Mean Standard Error Standard Error Median Median Mode 2.07 Mode Standard Deviation Standard Deviation Sample Variance Sample Variance Kurtosis Kurtosis Skewness Skewness Range Range Minimum Minimum Maximum Maximum Sum Sum Count 119 Count 120 9

10 CD control : Is there any difference between this A and B feature as measured? Descriptive Statistics ( from Excel) NORMSINV Normal Probability Plot - CD measurements A FORK 99.9% 99.4% 2 B FORK 97.7% % % % 0 50% % % % % % % Param eter 10

11 CD control : Is there any difference between this A and B feature as measured? Plot the data to determine a uniformity value: Outliers What are there: Real or measurement errors?? CD microns Fork A Intra-Wafer CD Uniformity Wafer Column left to right Row 1 Row 2 Row 3 Row 4 Row 5 Row 6 Row 7 Row 8 Row 9 Row 10 Row 11 Row 12 Row 13 Row 14 CD microns Fork B Intra-Wafer CD Uniformity Wafer Column left to right Row 1 Row 2 Row 3 Row 4 Row 5 Row 6 Row 7 Row 8 Row 9 Row 10 Row 11 Row 12 Row 13 Row 14 11