Nanospec Film Thickness Measurement System
Nanospec AFT Model 210
- General Information
- The NanoSpec is a tool that measures the depth of thin films on silicon. It can accurately measure film depths in the range from 100 to 500,000 Angstroms, or .01 to 50 microns. The tool acts as a diffraction-grating based spectrometer to measure the reflectance of films across the spectrum of light from 370 to 800nm wavelengths, and from this data, together with the known index of refraction dispersion values for both the film material and the silicon substrate, extrapolates the thickness of the film.
- Equipment Specifications
- Thickness range: 100 to 500,000 Angstroms
- Measurement Spot Sizes (spot diameter):
- 5x objective lens: 50 micron spot size
- 10x objective lens: 25 micron spot size
- 50x objective lens: 5 micron spot size
- Film Types:
- Oxide on silicon
- nitride on silicon
- Negative resist on silicon
- polysilicon on oxide
- Negative resist on oxide
- nitride on oxide
- Thin oxide on silicon
- thin nitride on silicon
- Polyimide on silicon
- positive resist on silicon
- Positive resist on oxide
- red resist on silicon
- Thick films
- (if silicon is not mentioned in the above as the substrate, then it is implied as the substrate to the stated 2-film system).
- Operating Proceedure
- Documentation Disclaimer
- DISCLAIMER—the operating procedure described here is a basic one, intended for novice users doing simple measurements. If you desire to use the Nanospec to do a more sophisticated measurement, ask the lab manager for the Nanospec operator’s manual. It's filed with the reference material and is labeled on the spine as AFT MODEL 210 / 210 VT / 210 UV, and says Nanometrics in teeny tiny print on the bottom.
- Activate the computer by flipping the red switch on the back of the box
- Activate the terminal with the switch on the base of the monitor
- Say no to ‘Enable Datalink?’
- The next prompt will ask ‘Is Wavelength 480?’ The current wavelength is displayed on the odometer-like counter on the front of the microscope assembly. If it says 480, hit YES. If not, hit NO, and enter in the displayed wavelength.
- Say NO to the refractive index option.
- Say NO to ‘Enable Printer?’
- How To Focus
- You will need to focus the microscope several times while using the Nanospec. The procedure is basically the same as with a standard microscope. Because it is generally difficult to focus on a reflective surface, the Nanospec has a ‘field diaphragm’ included in the microscope. When the field diaphragm is engaged, it constricts the size of the image that you can see through the eyepiece of the microscope. When you have focused the microscope correctly, the borders of the image you see should make a sharp-sided octagon. It’s important to KEEP THE FIELD DIAPHRAGM on while taking measurements. The only reason it should be disengaged is to aid in finding a specific spot on which to focus on the wafer. The control for the field diaphragm is a black slider-ring leading on the illuminator tube.
- The dot you see in the center of the eyepiece image needs to fit inside the feature that you’d like to measure. If it doesn’t, use a more powerful microscope objective to take your measurements.
- See the operator’s manual for more details on focusing.
- Preparation and Setup
- Allow 30 minutes for the machine to warm up, and then continue with the setup and calibration
- Place a bare silicon wafer on the stage. Follow the directions on the screen.
- See previous section for information on how to focus, if you haven't already.
- Press ENTER when complete
- Measuring Wafers
- select the correct program from the program list
- enter which objective lens you are using
- calibrate as directed with the reference wafer (a blank, clean wafer)
- focus on the feature of the wafer that you want to measure
- enter your sample ID
- hit MEAS when ready
- Decline the SEQS send
- For more info, see the Operator’s Manual
- Machine Shutdown
- Turn off the red switch on the back of the computer, and turn off the terminal. Store the sample wafer so it stays clean.
- The battery to the BIOS of the monitor terminal that interfaces with the Nanospec is pretty much dead, so the terminal settings that allow it to communicate with the Nanospec computer get wiped periodically. If this has happened, you will not see the startup screen when you turn the terminal on; you’ll only see a flashing cursor. To fix this, enter the terminal’s BIOS setup by holding down the SHIFT key and hitting the SETUP key. Once you’re in the setup menu, set the Terminal setting to ADD VP. Hit s, then e to save and exit, and restart the Nanospec.