Thin Nitride Measurement Example

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Johnathan Parks
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1 Thin Nitride Measurement Example GOAL: Get the most information from your data and analyze it properly to make the right decisions! Look at the data in multiple ways to understand your process better. The old saying is Let the Data or parts talk to you. 1

2 Thin Nitride Measurement Example Definition of Thin Nitride : sub 1000A thickness Film to measure: PECVD Silicon Nitride deposited on Silicon_ A nominal 450A nitride film thickness was deposited on fifteen silicon wafers using a Novellus Thickness and R.I. (refractive index n) was measured on an Optiprobe Model DUV and a Tencor Model tool Measurement data from the two measurement tools was then compared. 2

3 Thin Nitride Measurement works on the dispersion principle ( refractive index is a function of wavelength) and uses wavelength to determine thickness and refractive index. The Refractive index on is quoted at the 632 nm wavelength! A recipe was optimized to measure Thin Silicon Nitride thickness ( A) and refractive index. Summary of Tencor measurement data: Goodness GOF values of were obtained. Thickness range: A (sample dependent) Refractive Index range: ( inter wafer dependent) (632 nm) 3

4 Optiprobe Thin Nitride Measurement Optiprobe uses ellipsometry and BPR to determine thickness and refractive index. A recipe was optimized to measure Thin Silicon Nitride thickness ( A) and refractive index. Summary of Optiprobe measurement data: Thickness range: A (sample dependent) Refractive Index range: ( inter wafer dependent) 4

5 Recipe PCVD/Nitride/Thin Nitride - 5PT Validation and comparison to Optiprobe 15 wafer test Thickness Comparsion EXCEL FORMATED DATA Setup Wafer # Center UV 1050 Top Left Bottom Right Center Top Left Bottom Right

6 Recipe PCVD/Nitride/Thin Nitride - 5PT Validation and comparison to Optiprobe 15 wafer test Refractive Index Comparsion EXCEL FORMATED DATA Setup Wafer # RI CEN RI TOP RI LEFT RI BOT RI RIGHT RI CEN RI TOP RI LEFT RI BOT RI RIGHT

7 comparison to Optiprobe 15 wafer test Thickness Comparsion Always look at data graphically first: EXCEL Plot Thickness A Silicon Nitride Thickness measurements Vs Optiprobe Center UV 1050 Top Left Bottom Right Center Top Left Bottom Right Wafer # What can we say about this data? 7

8 comparison to Optiprobe 15 wafer test Thickness Comparsion Always look at data graphically first: EXCEL Plot Thickness A Silicon Nitride Refractive Index measurements Vs Optiprobe Wafer # RI CEN RI TOP RI LEFT RI BOT RI RIGHT RI CEN RI TOP RI LEFT RI BOT RI RIGHT What can we say about this data? 8

9 Recipe PCVD/Nitride/Thin Nitride - 5PT Validation and comparison to Optiprobe 15 wafer test Thickness Comparsion EXCEL Data Analysis 9

10 Recipe PCVD/Nitride/Thin Nitride - 5PT Validation and comparison to Optiprobe 15 wafer test Thickness Comparsion EXCEL Descriptive Statistics 10

11 Recipe PCVD/Nitride/Thin Nitride - 5PT Validation and comparison to Optiprobe 15 wafer test Thickness Comparsion EXCEL Descriptive Statistics Statistic Center UV 1050 Top Left Bottom Right Center Top Left Bottom Right Mean Standard Error Median Mode Std Dev Sample Variance Kurtosis Skewness Range Minimum Maximum Sum Count

12 Recipe PCVD/Nitride/Thin Nitride - 5PT Validation and comparison to Optiprobe 15 wafer test Thickness Comparsion Statistic UV 1050 SiN Mean Standard Error Median Mode Standard Deviation Sample Variance Kurtosis Skewness Range Minimum Maximum Sum Count NORMSINV Normal Probability Plot - Thin Nitride Measurements % % % % % % 0 50% % % -1.5 UV 1050 SiN 6.7% % % % Thickness A 12

13 Recipe PCVD/Nitride/Thin Nitride - 5PT Validation and comparison to Optiprobe Optiprobe recipe variance significantly less than recipe STATISTICAL TESTS: F- test and T-test on Thickness data REASON : Unknown UV 1050 SiN Statistic Mean Variance Observations df F P(F<=f) one-tail F Critical one-tail Variances are significantly different! 2.5% chance of incorrectly rejecting Null that variances are equal t-test: Two-Sample Assuming Unequal Variances Statistic UV 1050 SiN Mean Variance Observations Hypothesized Mean D 0 df 141 t Stat P(T<=t) one-tail E-41 0% chance of incorrectly rejecting Null that Means are equal t Critical one-tail P(T<=t) two-tail E-40 t Critical two-tail

14 Recipe PCVD/Nitride/Thin Nitride - 5PT Validation and comparison to Optiprobe 15 wafer test Refractive Index Comparsion Statistic UV 1050 SiN Mean Standard Error Median Mode Standard Deviation Sample Variance E E-05 Kurtosis Skewness Range Minimum Maximum Sum Count NORMSINV Normal Probability Plot - Thin Nitride % % % % % % 0 50% % % % -2 RI 2.3% -2.5 RI 0.6% % Refractive Index 14

15 Recipe PCVD/Nitride/Thin Nitride - 5PT Validation and comparison to Optiprobe 15 wafers STATISTICAL TESTS: F- test and T-test on Refractive Index data show improved variance with Optiprobbe Recipe as compared to REASON : Unknown F-Test Two- Sample for Variances RI RI Mean Variance 2.970E E-05 Observations t-test: Two-Sample Assuming Unequal Variances RI RI Mean Variance 2.970E E-05 df Observations F P(F<=f) one-tail E-20 F Critical one-tail Variances are significantly different! 0% chance of incorrectly rejecting Null that variances are equal Hypothesized Mean Diffe 0 df 81 t Stat P(T<=t) one-tail E-57 t Critical one-tail P(T<=t) two-tail E-57 t Critical two-tail

PROJECT PROPOSAL: OPTIMIZATION OF A TUNGSTEN CVD PROCESS

PROJECT PROPOSAL: OPTIMIZATION OF A TUNGSTEN CVD PROCESS Heather Brown and Brian Hesse IEE 572 December 5, 2000 The tungsten chemical vapor deposition (WCVD) process has been used in the semiconductor