Woollam M2000 Spectroscopic Ellipsometer, woollam

The Woollam M2000 is a spectrometer which will measure phase changes in polarized light to estimate the thickness and optical constants of films.

Contents

Picture and Location

Background

Process Capabilities

Cleanliness Standard

Performance of the Tool

The System

Contact List and How to Become a User

Contact List

Training to Become a Tool User

Operating Procedures

Process Monitoring and Tool Qualification

Picture and Location

 Woollam M2000

 

Background

The Woollam tool uses ellipsometry to characterize thin films.  Ellipsometry detects the phase change in polarized light as it reflects from or transmits through samples.  The Woollam does not directly measure thickness and optical constants, but rather uses collected data to solve models which estimate the thickness and optical parameters of interest.  The general sequence of operation is: 1) Measure, 2) Create Model, 3) Fit, 4) Results.

 

The Woollam measures Ψ and Δ which characterize the change in polarization as the light is reflected from the surface.  Ψ characterizes the amplitude and Δ characterizes the phase difference.

 

Process Capabilities

Cleanliness Standard

 The Woollam M2000 Spectroscopic Ellipsometer appears in all three equipment groups (clean, semiclean, and gold).

 

Performance of the Tool

What the Tool CAN do

 

What the Tool CANNOT do

 

The Woollam is capable of using variable angles of incidence.  In order to optimize the reflection from the surface only (and not the substrate), measurements around the Brewster angle of the substrate is recommended to enhance sensitivity to film parameters.   Multiple angle measurements can be used to improve confidence in the final answer.

The Woollam measures reflected light across the 210-1600 nm spectrum.  The spot size varies with angle of incidence from 1.1-11.5mm (It is 2mm normal to the surface).

 

The System

 

Contact List and How to Become a User

Contact List

The following people make up the Tool Quality Circle:

 

Training to Become a Tool User

  1.   Read all material on the SNF website concerning the Woollam M2000 Spectroscopic Ellipsometer.
  2.   Shadow lab users on Woollam.  After this step, the user should be familiar enough with the equipment to be able to run the equipment on their own.
  3.   Contact Michelle Rincon (mmrincon at stanford dot edu) for qualification.  The final certification will consist of 2 tests: 1) written quiz, and 2) in-lab oral exam.

 

Operating Procedures

The software has uses 6 different windows to perform different functions.  First, the Hardware window is used to collect the data.  After data collection the Hardware window can be closed and the general work flow is in a counter clockwise direction starting in the upper right hand corner of the screen with the Data window.  As you click on each window, a different set of menu instructions is shown.  Right clicking in any window also shows the list of menu options for that window.

 

Typical work flow:

  1. Enable in Badger.
  2. Turn on the lamp with “Lamp Ignition” button.
  3. Load wafer on chuck.  Turn on vacuum switch.
  4. Logon to computer screen.
  5. Open WVase32 software.
  6. In Hardware Window:
  1. Align Sample- this will find the center of a 4-in wafer.
  2. Spectroscopic Scan -> Acquire data.
  1. Verify Data is visible in Data window and curves displayed in Graph Window.  Default settings for graph are Ψ and Δ on the y-axes and nm on the x.  Right clicking on the graph will show options for changing the data that is graphed and the axes.
  2. Create model.
  1. Generate Data
  1. Solve for fit parameters
  1. Modify model if necessary, then repeat steps 8 and 9 until you are satisfied with the answer.
  2. Turn off vacuum and remove wafer.
  3. Turn off lamp by powering down system, waiting for lights to go off, then turning power back on.  Lamp ignition light will remain off.
  4. Close Vase software and lock computer screen.

 

Some options (more frequently used options - many more exist and please feel free to document any helpful procedures that might be useful to lab members!):

  1. Transmission Scan instead of Spectroscopic Scan.  Transmission scans require that the wafer be set perpendicular to the chuck.  SNF does not have a jig available for users but many users fashion their own out of lab-approved materials.
  2. Some films will not have the optical constants in any of the tool databases.  Modeling of the films as Cauchy layers, EMA layers or GENOSC layers can be done as well.  Please contact staff for training if you need help.

 

Process Monitoring and Tool Qualification

A calibration wafer is run after lamp changes and for error recovery. Monthly calibration checks are to be scheduled.