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iLab Name: Stress machine

iLab Kiosk: BRK Metrology Core
FIC: Shared
Owner: Rich Harlan
Location: Cleanroom - R/S Chase
Maximum Wafer Size: 8"/200 mm

Overview

General Description

The Thin Film Stress Machine is a non-destructive testing tool used to analyze the stress of thin films. The stress machine analyzes the radius of curvature of your whole wafer prior to the film being deposited. Then after film deposition, the stress machine reanalyzes your sample to compare to the original. This change in radius of curvature will then result in a film stress value in the units of MPa.

Specifications

• Capable of 4, 5, and 6 inch whole wafers
• Can measure film stress from ambient to 500°C
• Can measure film stress over a period of time
• Capable of graphing time vs stress, and temp vs stress
• Capable of measuring deflection of the substrate
• Nitrogen reduces oxidation during heating
• CDA can assist in cooling

Technology Overview

Sample Requirements and Preparation

Note: You must know your substrate thickness and film thickness to achieve a proper stress value

Standard Operating Procedure

 1.  SAFETY REQUIREMENTS

1. 1. Safety glasses must be worn whenever in the cleanroom, except when using a microscope or when wearing protective goggles.
   2. This tool utilizes two lasers, 670nm l and 780nm l, which are enclosed within the tool. Do not remove any covers or defeat any interlocks
   3. This tool is capable of heating the sample chuck to 500°C. Care must be taken when using this feature to prevent burns

 2.    EQUIPMENT

1. 1. FLX-2023-S Thin Film Stress
      i) Toho Technology Corp, model FLX-2023-S, S/N 0708-8114
      ii)     Heated chuck capable of reaching 500°C (idles at room temperature)
      iii)    Wafer Locator Fixtures that correspond to the 3-pins at 120°intervals
              (1)   Square locator fixture used with standards
              (2)   100-mm (4-inch)
              (3)   125-mm (5-inch)
              (4)   150-mm (6-inch)
      iv)    Hot Chuck Cover
      v)     Standards;
              (1)   Curve Mirror Standard (20.069-meter radius, S/N 0608-0118)
              (2)   Flat Mirror Standard (S/N 0608-0118)

 3.   TOOL CONFIGURATION

4.    CYCLE OF OPERATION

1. Verify the tool is powered up and ready to use. Refer to Section 6 for the Start-up procedure.
2. Verify the Baseline performance check has been completed prior to measuring any samples.

      BASELINE

1. Select the square locator fixture for the baseline measurement.
2. Open the front door (Figure1) and place the square locator fixture in the measurement chamber making sure the fixture is aligned to the three (3) alignment pins in the chuck.
3. Position the flat mirror standard inside the square so the mirror is against the back and right-side edges of the locator fixture shown in Figure2.
4. Close the front door.
5. Select “Process programs” in the “Edit” dropdown window:  
6. Click on the “Load” button
7. Select the “mirror670.PRC” process program
8. Select the “Measure” dropdown at the top of the page
9. Select the “First (no film)” option
10. Type in a unique name next to “file:” and a unique number next to “ID”
11. Select the “Measure” button
12. The tool will scan the standard and display the Radius value as well as the bow value (red font) displayed on the graph.
13. Open the door to remove the flat mirror
14. Exchange the flat mirror with the “R=20.069M” curved mirror so the mirror is positioned against the back, right corner of the locator fixture as shown in Figure2.
15. Close the front door
16. Scan the curved standard and record the value
17. Select “Process programs” in the “Edit” dropdown window: 
18. Click on the “Load” button
19. Select the “mirror780” process program
20. Select the “Measure” dropdown at the top of the page
21. Select the “First (no film)” option
22. Type in a unique name next to “file:” and a unique number next to “ID”
23. Select the “Measure” button
24. The tool will scan the standard and display the Radius value as well as the bow value (red font) displayed on the graph.
25. Open the door to remove the flat mirror
26. Exchange the flat mirror with the “R=20.069M” curved mirror so the mirror is positioned against the back, right corner of the locator fixture as shown in Figure2.
27. Close the front door
28. Scan the curved standard and record the value

      SAMPLE MEASUREMENT

1. Open the front door and verify there are no other locator fixtures inside the tool.
2. The 100mm locator fixture has several different orientation options, most will use 0°, record the orientation used. The same orientation must be used during the second measurement to get usable measurements. There is a black line marked at the 3:00 position for the 0° orientation.
3. Place the wafer sample inside the locator fixture with the flat aligned with the ring and the wafer lying flat in the measurement chamber with the polished side facing up.
4. Close the front door.
5. Select “Process programs” in the “Edit” dropdown window: 
6. Click on the “Load” button
7. Select the desired process program
8. Select the “Measure” dropdown at the top of the page
9. Select the “First (no film)” option
10. Enter (and remember) the “File:” name that is entered (example 200202.DAT)
11. Enter (and remember) the “ID:” number that is entered
12. Press the Measure button
13. Remove the substrate and grow/deposit the film.
14. Place the wafer in the fixture using the same orientation
15. Select the “Edit” dropdown window and select “Process Programs”
16. Select the same recipe used for the first/no film measurement
17. Select the “Measure” dropdown and select “Single”
18. Enter the same filename used for the first measurement
19. Enter the same ID that was used before
20. Enter the film thickness
21. Press the measure button

The stress value will be displayed on the top graph in MPa units

This is the TOHO Stress Measurement System Control Chart:

Questions & Troubleshooting

Process Library

References