Gaertner Stokes Ellipsometer
Contents
1. Film Parameter Fields film stack information white background Thickness 1 Estimated top layer film thickness to be measured Nf 1 Estimated top layer film refractive index to be measured Kf 1 Estimated top layer film extinctive coefficient to be measured Enter O for transparent film Thickness 2 3 4 Underlayer film thicknesses if exist Needs to be measured before depositing the top layer film Nf 2 3 4 Underlayer film refractive indices if exist Needs to be measured before depositing the top layer film Kf 2 3 4 Underlayer film extinctive coefficient if exist Enter 0 for transparent film Ns Ks Refractive index and extinctive coefficient of the substrate Calculation Modes or Combinations selection of Thickness Nf and Kf buttons do not confused with the Film parameter Field described in the above section Thickness 1 Calculate top layer film thickness using the refractive index entered in Nf1 Field Thickness 1 amp Nf 1 Calculate both the thickness and refractive index of the top layer film ellips 9 3 4 Chapter 8 35 Thickness 1 Nf1 amp Autofix Nf1 Calculate both the thickness and refractive index of the top layer film if the refractive index calculation is stable same as Thickness 1 amp Nf 1 Otherwise use the refractive index entered in Nf1 field same as Thickness 1 Thickness 1 amp Thickness 2 Calculate the thickness of top two layer films using the refractive indices entered in N2. All the measurements are done using the GEMP software 7 0 Statistical Process Data N A 8 0 Available Processes amp Process Notes 8 1 8 2 Available Programs 8 1 1 Thin Oxide Default program of GEMP software It can be used to measure a single layer oxide film about 500A thick 8 1 2 Thin Nitride Default program of GEMP software It can used to measure a single layer nitride film about 10004 thick Process Notes 8 21 The LSE Stokes Ellipsometer is capable of measuring the top film thickness refractive index of a four layer film stack To do so the film thicknesses and refractive indices of the lower layers need to be measured before the top layer film is deposited 8 2 2 The refractive index measurement is unstable in the thickness range within about 25 of zero thickness or period value If the oxide film to be measured is under 700 A the refractive index should be entered into the computer before measurement 8 2 3 The best film thickness for refractive index measurement is about the half the period value e g 1400 A for Oxide and 900 A for nitride 9 0 Equipment Operation 9 1 9 2 Equipment Description The LSE Stokes Ellipsometer is comprised of the ellipsometer itself and table top PC running GEMP software running under WINDOWS OS for film thickness and refractive index calculation See Figure 11 1 for the physical layout of the ellipsometer and Figure 11 2 for the display screen of the GEMP software T
3. F7 Print Measured Data Measured Data F10 Stats F2 Thin Nitride F8 Measure amp Calculate v 0 0001 A 00001 F3 Shortcut 3 Measure Calculate Thick A Au DP 3 F4 Shortcut 4 F3 Adjust Sample T able HER Timed Measurement Measurement Statistics Figure 11 2 GEMP Measurement amp Calculation Window ellips Chapter 8 35 TMAX Table Height Adjustment for Maximum Power TILT Sample Table Tilt Adjustment Always adjust table tilt prior to adjusting table height Figure 11 3 Sample Stage Alignment Window xn M Jil C EEEHREEO TILT ADJUSTMENT T ES eem X PLANE e The a VERTIC L ADJUSTMENT WHEEL TILT ADJ STMENT Se Y PLANE Figure 11 4 Sample Stage Layout ellips Chapter 8 35 120 Appendix Measurement Comparison of STOKE Ellipsometer NanoDUV and Nanospec Nitride Wafer ID T9 Fix RI entered 1 456 Calculate RI RI Measured Fix RI computer default 1 456 Calculate RI RI Measured Fix RI computer default 1 456
4. Marvell Nanofabrication Laboratory University of California Berkeley Berkeley Microfabrication Laboratory abb Lab Manual dE Marvell NanoLab Member login Lab Manual Contents MercuryWeb Berkeley Microlab 1 0 2 0 3 0 4 0 5 0 6 0 Chapter 8 35 Gaertner Stokes Ellipsometer ellips 386 Title Gaertner Stokes Ellipsometer Operation Purpose The LSE Stokes Ellipsometer made by Gaertner Scientific Corporation uses the patented StokesMeter technology to measure the thickness and or the refractive index of transparent films There is no moving parts and no modulators in this system It uses a 6328 A HeNe laser at a 70 incidence angle The sample stage can accommodate up to 300 mm size wafers but only the center 150 mm can be measured at this time as the wafer stage is stationary at this time no X and Y stage movements available GEMP Windows software can calculate the film thickness and refractive index of a layer on a substrate or on top of a film stack that consists of three layers with known film thicknesses and refractive indices The measurement and calculation time of a single layer film is fast only a fraction of a second Scope This document covers sample stage adjustment and film measurement using GEMP software Applicable Documents Revision History LSE Stokes Ellipsometer User Manual 7109 C370A Gaertner Scientific Corporation clean room copy at the tool location Definitions amp Process Te
5. You can find the period value of the measured film from the list Shortcut Buttons These buttons can be link to film stack model files Return Button Closes the measurement amp Calculation Window and return to the print area window 10 0 Troubleshooting Guidelines 10 1 Problem No laser light spot on the sample stage Solution Laser malfunction Report problem 10 2 Problem The calculated refraction index or the underlayer thickness is far from the expect value or not repeatable Solution The film thickness is within 25 of zero thickness or period value Change the film thickness ellips Chapter 8 35 11 0 Figures amp Schematics Top Module Contains Alignment Laser Diode and Position Sensor Entrance Aperture on Inside Plate Sample Table Left Module Right Module Contains Measuring Contains Laser StokesMeter Detector Base Plate Figure 11 1 LSE Stokes Ellipsometer Physical Layout Measurement and Calculation Thin Film Model Model File Thin Nitride tfrn Load File Save File Serial No 1862 4K Thickness 1000 Thickness 2 0 Thickness 3 0 Thickness 4 0 Print Thin Film Model Enlarge Psi Delta Map Measurement and Calculation Thick Pmtr2 Psi Delta DP Reads 25 permeas F5 Start tMeas 0 we of of of of o Interval 0 sec FE Stop Print Stats Max 0 0 0 0 Clear Stats Ma g D J StdDev 0 0 0 0 0 F1 Thin Oxide
6. f1 and Nf2 field Thickness 1 amp Kf 1 Calculate the thickness and the extinctive coefficient of the top layer film If used to measure the poly silicon film on oxide the thickness of the oxide film must be precisely measured first The thickness of the poly silicon film should not be over 800A Substrate Ns amp Ks Calculate the refractive index and extinctive coefficient of the bare substrate Make sure there is no native oxide film on the substrate Click Save File button to save your film stack model all save film stack models have file extension tfm 9 4 Other Operation Buttons 9 4 1 9 4 2 9 4 3 9 4 4 9 4 5 9 4 6 9 4 7 9 4 8 9 4 9 9 4 10 9 4 11 Print Measured Data Button Print the measured data to the print area window in the background Measure Button Measure the sample Y and A no calculation Calculate Button Calculate the film properties using displayed Y and A which can be entered manually Enlarge Psi Delta Map Button Enlarge the map for what if analysis Enable Stats Button Calculate and display the measurement statistics Print Stats Button Prints the displayed statistics table to the print area window Clear Stats Button Clear and fill the statistics table with zeors Print Measured Data Button Print Y and A and calculated solutions to the print area window Pint Listing Button Print the list of 10 film thickness that correspond to the measured Y and A to the print area window
7. here are two lasers used One from top module for sample alignment The other from the left module for measurement Both of them can be clearly seen at the center of the sample table CAUTION To prevent any possible eye damage refrain from looking into the laser beam or its specular reflection from wafers Measurement Procedures 9 2 1 Enable the LSE Stokes Ellipsometer ELLIPS 9 2 2 Check the both lasers are ON and the center of the sample stage is illuminated 9 2 3 Place your sample wafer on the sample stage You may not see the lasers light spot because of the film on the sample Note the measuring spot is at the center of the stage Sample Alignment 9 2 4 Log onto the PC Double click the GEMP icon to start the software Click the ellipsometer icon on the top of the screen or use the drop down menu under Ellipsometer Measurement and Calculation to open the Measurement and Calculation Window Figure 11 2 9 2 5 Click the Adjust Sample Table button on the left lower corner of the Measurement and calculation screen A new window will pop out to assist you see Figure 11 3 ellips 9 3 9 2 6 9 2 7 9 2 8 9 2 9 9 2 10 9 2 11 9 2 12 9 2 13 Chapter 8 35 Locate the X and Y plane adjustment knobs and vertical adjustment wheel below the sample stage see Figure 11 4 Adjust the sample tilt by turning the X and Y plane adjustment knobs until the target cross is centered in the box shown under the TILT adjustme
8. nt section of the screen Adjust the sample stage height by turning the vertical adjustment wheel until the two horizontal cursors shown on the left side of the screen line up with each other long bar is even with the shorter bar Click OK button to return to the Measurement and Calculation Window Film Measurement At the top of the Measurement and Calculation Window enter the film stack information for your layers or load a stack model file that has already been stored in the PC Skip this step if you are measuring a single layer of thin oxide or nitride For a single layer enter a rough estimate of your film thickness in the thickness1 field The refractive index of the film will need to also get entered or calculated by clicking on Nf1 button then entered in the Nf1 field Click Measure amp Calculate button to perform film thickness measurement The measured film thickness will appear in the Measured Data windows There are two predefine recipes for Thin Oxide and Thin Nitride that can be used by a click of a button at the lower left side of the screen These can be used for single layer oxide or nitride measurement Please do not modify these recipe Remove your sample and logoff the WINDOWS when you are done Film Stack Model Set Up 9 3 1 9 3 2 9 3 3 Instrument Parameter Fields software default do not change 70 Laser incidence angle A 6328 A HeNe laser wavelength Ambient N 1 refractive index of air
9. rminology 5 1 Ellipsometry Characterization of the optical properties of materials by examining the change in polarization of a reflected or transmitted beam of light By studying the complex reflection transmission ratio of the TM TE electromagnetic field components the index of refraction and thickness in a thin film optical system may be measured This program calculates two parameters W psi and A delta derived from the measured light wave reflection transmission coefficients placed in Fresnel equations and iteratively solves for the thicknesses and or index of refraction 5 2 Refractive Index n The real part of the optical constant of a material It defines the phase velocity of light in the material u c n where u is the speed of light in the material and c is the speed of light in vacuum 5 3 Extinction Coefficient k The imaginary part of the optical constant of a material It is directly related to the absorption of a material It is related to the absorption coefficient by a 4 T k where a is the absorption coefficient and A is the wavelength of light Safety Following are the general safety guidelines in the lab as well as the specific safety rules 6 1 Laser Safety Observe laser caution to prevent any possible eye damage Do not look into the laser beam or its specular reflection ellips 6 2 Chapter 8 35 Electric Shock To prevent electric shock do not change any switch settings and plug connections
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