Film Thickness Measurement Julian Peters Joe Fitzmyer Brad Demers P06402

Agenda Project Overview & Background Needs, Requirements, and Specifications Concept Development Interferometry Background System Operation Analysis Bill of Materials Anticipated Design Challenges Senior Design II

Project Overview - Background Meniscus Experiment in RIT Thermal Analysis Lab Figure 1: Moving Meniscus ExperimentFigure 2: Heater surface and water nozzle detail

Project Overview - Background Meniscus Experiment in RIT Thermal Analysis Lab Figure 3: Operation of experiment Heated, rotating copper cylinder Meniscus Evaporation Direction of Rotation

Project Overview - Background Meniscus Experiment in RIT Thermal Analysis Lab – Unanswered Questions: – Is there a film of adsorbed water left behind the moving meniscus? – How far does it extend? – What is its thickness?

Project Overview – Sponsor’s Major Needs Ability to determine existence and thickness of film Cost-effectiveness Ability to operate in a “dirty” environment Accuracy, but not as demanding as semiconductor applications

Key Requirements Must differentiate between film and no film Ability to determine thickness profile of film greatly desirable Must be able to take measurement quickly Must not require constant input from user

Specifications & Targets Positioning Accuracy – ± 0.25° Positioning Precision – ± 0.25° Film Thickness Accuracy – ± 5 μ m Film Thickness Precision – ± 5 μ m Measurement Time – 30 minutes

Concept Development Technologies Considered: – Physical Measurement Thermal Cycle Testing Profilometry – Acoustic Measurement Acoustic Reflections (e.g. ultrasound) – Optical Measurement Ellipsometry Interferometry

Concept Development Eliminating Concepts: – Physical Measurement Lack of accuracy Will disturb film More sensitive to surface irregularities – Acoustic Measurement Accuracy is a concern Implementation is not clear

Concept Development Differentiation Among Optical Methods Figure 4: Decision Matrix

ii Film Surface Substrate Surface 1) Light is emitted from the laser diode. 2) Two reflections take place: part of the beam reflects from the film surface, part of it continues through the film and reflects from the substrate surface. 3)The two reflected beams recombine. The difference in the path length taken by the two beams manifests itself as a phase difference, which can cause attenuation of the beam intensity. 4) The recombined beam is collected at a sensor. The intensity is measured, and can be compared to the intensity of the original beam. Interferometry in a Nutshell Figure 5: Interferometry Basics

System Operation User initializes the measurement through a simple GUI Stepper motors position goniometers at a range of angle increments Photodiode captures a portion of light energy emitted at each angle increment LabView controller inputs position data to stepper motors LabView plots captured data and outputs measured thickness as well as error or confidence level of the measurement

Block Diagram Figure 6: Information and control flow through system PC Control HardwareGoniometer Stepper Motors Laser Diode Power PhotosensorLabView Data Collection Hardware Operator Light reflected from surface Information Control

Motors Goniometers Laser diode Photodiode Anticipated System Operation Figure 7: Assembly at 55° incident angle

Figure 8: Assembly at 45° incident angle

Figure 9: Assembly at 35° incident angle

Analysis of Design MATLAB code written to simulate reflectance response Data from numerical experiments – Determine appropriate wavelengths – Analyze experimental data Most easily identified parameter of data is the frequency of oscillations

Sample MATLAB Results Figure 10: Oscillatory Reflectance Response

Sample MATLAB Results Figure 11: Non-Oscillatory Reflectance Response at Zero Film Thickness

MATLAB Code Verification Figure 12: Comparison of WVASE32 and MATLAB Results

Off-the-Shelf Components Laser diode: TIM-206Goniometers: GNL18/M-Z6 Photodiode: S Motor Controller: DCX-PCI100

Bill of Materials Figure 13: Anticipated Costs

Anticipated Design Challenges Light Source – Beam divergence – Suitability of wavelength to film thickness – Consistency of intensity Photodiode – Must accommodate beam divergence – Ability to differentiate changes in intensity of the beam from random noise

Anticipated Design Challenges Positioning Equipment – Accuracy – Repeatability – Synchronicity Equipment Mounts – Must be accurately machined to avoid loss of overall accuracy of system

Anticipated Design Challenges PC Interface Hardware – Interface with positioning equipment must provide program with position information – Must preserve the accuracy of the rest of the system Data Interpretation Programming – Must be able to “fit” experimental data to simulated data as accurately as possible – Some measure of confidence of fit would be useful to user

Anticipated Design Challenges Specific Application to Mensicus Experiment – Varying optical properties of surface due to discoloration, physical imperfections, etc. – Misalignment of beam due to surface imperfections – Alignment of rotating copper surface

Senior Design II Plan Order & fabricate parts Assemble functional setup as soon as possible Test setup against known films produced by the RIT Microelectronic Engineering Dept. Develop code throughout quarter Modify and revise design as needed and as problems are encountered

Senior Design II Plan Order & fabricate parts Assemble functional setup as soon as possible Test setup against known films produced by the RIT Microelectronic Engineering Dept. Develop code throughout quarter Modify and revise design as needed and as problems are encountered

Senior Design II Schedule Figure 14: Senior Design II Gantt Chart

Any Questions?

Interferometry Analysis for s-polarization for p-polarization for s-polarization for p-polarization