Microelectronics Research Center

Questions, comments, complaints, bugs about this page? We would like to hear from you.

Tencor Alpha Step Profilometer

Table of Contents:
I: Introduction
II: Machine Specifications
III: System Components
IV: Operating Instructions
V: Creating a Recipe
VI: Troubleshooting
VII: DO's and DON'Ts
VIII: Check-off requirements

I. Introduction

The Alpha-Step is one of two profilometers in the class 1000 photolithography bay. The profilometer measures the surface profile of a sample by recording the vertical position of a stylus vs. its horizontal position as the stylus scans across a surface. It does not directly generate the film thickness. To measure the thickness of a film, a step that is comparable to the film thickness must be produced before the measurement. This can be done in many ways, such as scratching the film with a knife (the substrate must be harder than the knife), cover part of the sample with a slide during film deposition, etc.

II. Machine Specifications

Materials allowed in this system:

  1. All inorganic materials
  2. Properly cured polymers -- uncured photoresist is NOT allowed

IF YOU WANT TO PROCESS ANY OTHER MATERIAL, YOU MUST GET APPROVAL FIRST (SEE FAQ).

III. System Components

  1. System
  2. Stylus
  3. Sample Holder
  4. Printer

IV. Operating Instructions

  1. Loading a sample
    1. Login to the access controller box
    2. Use the knobs on the left side to move the stage towards you.
    3. Put the sample you want to examine on the stage.
    4. Move the sample under the microscope.
  2. Operating the system
    1. Press F1 to edit the recipe. You can either load a recipe or just set the parameters you want to use. Press ESC to leave the recipe editor. You can return to and switch between recipe editor and surface profile display window by pressing ESC any time.
    2. Press the X-Y key. After a few seconds, the image captured by a microscope above the stage will be displayed on the screen. If you see a dark area, the stage may be severely out of focus at this point. You will also notice that the illumination around the tip increases.
    3. Press the up arrow on the keyboard. This will make the stylus move out of the way if it isn't already. Visually check the area under the stylus and make sure that there is enough clearance between the stylus and the stage. It is important to do this every time before you load or unload your sample so as not to damage the stylus.
    4. You may need to press the down arrow key to raise the stage to get it into focus. Once it is in focus, press the up arrow key briefly to raise the stylus. Never move the stage with the stylus down!
    5. Move the stage into position using the knobs on the left side. You can rotate the stage too (just turn it by hand).
    6. After you have the stage lined up, press the start key. The stylus will come down, move across the sample and then go up. Then the results will be displayed.
    7. You may want to change the recipe settings or move the sample using the instructions above to get the results you want.
    8. Usually, the scan will not be level. You can level it by pressing F11 (LEVEL), and using the trackball to move the two leveling lines to two points on the graph that should be at the same height. You can switch lines by pressing space. When you have the lines in position, press LEVEL again. The display will be leveled.
    9. You can use the trackball to move two vertical lines on the screen. Use the space key to select which line you are moving. The height difference between the lines is displayed on the left side of the display.
    10. For any of the four cursors (or vertical lines, two for leveling and two for measurement), you can use up arrow to split the line into two and the computer will display the average results in the range confined by the two lines on the left side of the screen; you can reduce the two lines to one by keeping pressing down arrow.
    11. You can zoom in on a given area by pressing F12 (ZOOM), using the trackball to choose the left bottom anchor point first and press F1, then choose the right top point to define the area to zoom in and pressing F12 again. (You can also follow instructions on the screen under the surface profile graph).
    12. If you want a printed copy of the screen, press PRINT SCREEN or Ctrl-P. After a few seconds, the printer will start printing.
  3. Unloading a sample and logging off
    1. Use the knobs on the left side of the system to bring the sample holder all the way out from under the microscope
    2. Rotate the holder so that the sample is facing you
    3. Gently remove sample with tweezers.

V. Creating a Recipe

All the parameters are shown on the recipe page. Here is a term-by-term explanation of the recipe page.

  • Recipe ID: the name which you want to save the recipe as
  • Horizontal Units: you can choose English or Metric
  • Scan Length: the length over which the stylus will scan across the surface (0.01mm-10mm)
  • Scan Speed: the speed at which the stylus will scan (0.002-0.2 mm/s)
  • Scan Time: Scan Length divided by Scan Speed
  • Sampling Rate: the higher the sampling rate, the higher the horizontal resolution (50, 100, 200Hz)
  • Horizontal Resolution: determined by the sampling rate
  • Multi-Scan Average: if a number larger than 1 is chosen, the machine will perform several scans and the computer will average the results; the number of scans can be from 1 to 10
  • Segmented: if a segmented scan is needed (Yes or No)
  • No. of Segments: this term is shown only when the Segmented is chosen as Yes; the number of segments in the scan range can be from 1 to 10
  • Spacing length: this term is shown only when the Segmented is chosen as Yes; the spacing length is the distance between the starting point of one segment and the starting point of the next segment
  • Stylus force: how much force the stylus is exerting on the sample during measurement; this parameter can not be changed
  • Contact Speed: how fast the stylus will approach the surface before the scanning starts; the scale is from 1 to 10
  • Vertical Units: you can choose English or Metric
  • Vertical range/Resolutions: two options are available, 300um/25A and 13um/1A; it is suggested that the larger range be tried first before attempting to use the smaller range
  • Profile type: centered, outward or inward; most of the time, all three options can work; it only matters when the surface unevenness is approaching the vertical range limit
  • Vertical Display Scale: always choose Auto
  • The remaining terms are related to the display and captioning of the surface profile graph

VI. Troubleshooting

Q:The machine does not respond when I press the keys. What do I do?

A: Check if you are logged into the machine. Check if the machine is printing or relocating the stylus after scanning; the machine will not respond to the keyboard during printing or stylus relocation. If you are logged in and the machine is neither printing nor relocating the stylus after scanning and the keyboard is not responding, the machine may need to be restarted. REPORT THIS PROBLEM TO A STAFF MEMBER; DO NOT ATTEMPT TO RESTART THE MACHINE WITHOUT PERMISSION.

Q:I can not see anything on the screen after I press the X-Y key. What's going on?

A: The microscope is probably out of focus; press the down arrow to bring the stage in focus Check if the illumination under the microscope is on; if it is not, the lamp may need to be replaced; contact a staff member at this point

Q:It seems that the stylus is not touching the surface or it is only producing random noise - Why?

A: Check if your sample is moving during scanning (See below if the sample is moving) Check if the vertical range and profile type that you have chosen is suitable for the surface roughness of your sample; make necessary changes if you think current settings are not suitable Try to adjust the positions of the sample and measure again If the problem still cannot be solved, the machine may need to be restarted; REPORT THE PROBLEM TO A STAFF MEMBER; DO NOT RESTART THE MACHINE WITHOUT PERMISSION

Q:My sample is moving with the stylus during scanning - why?

A: Your sample is not generating enough friction to resist the drag by the stylus; you can fix your sample on a glass slide with adhesive tape - then make the measurement again.

VII. DO's and DON'Ts

DO

  • look into the area under the stylus and make sure that there is enough clearance before loading and unloading samples
  • make sure that your sample is clean and will not contaminate or damage the stylus

DO NOT

  • change any parameters other than those displayed on the recipe page.
  • move the stage when the stylus is touching the sample
  • make measurements on samples with sharp changes of height that are beyond the measurement range of the machine.
  • restart the computer without permission from cleanroom staff.

VIII. Check-off requirements

You must be able to demonstrate the following to be checked off on this system:

  1. Load a sample
  2. Unload a sample
  3. Modify recipe parameters
  4. Perform a scan
  5. Level scan data
  6. Handle keyboard-non-response error
  7. Print a data screen
  8. Know allowed and nonallowed materials
  9. Know the approximate height of your sample