Electrode Parallelism – Systems with Domed Lower Electrodes
Electrode parallelism and gap calibration is required each time either of the system electrodes is changed or there is a problem with the wafer uniformity. This procedure should be performed by factory trained technicians or by Lam Research Field Service Engineers only.
The model used at PCC is 4520. It is a part of the 4500 series. It has a lower clamp and a domed lower electrode.
Reference Documentation:
1. Procedure, Chamber Vent – Automatic 4500 Systems.
2. Procedure, Lower clamp removal
3. Procedure, Plunger Attachment Plate Removal – 4500 Systems +
Procedure, Confinement Ring Change – 4500 Systems.
4. Procedure, Process chamber Cleaning – 4500 Systems, or
Equipment Required:
1. Full solvent gear – arm guards, apron, self-contained breathing apparatus, goggles, and solvent compatible gloves. (Not applicable at PCC)
2. Surgical gloves.
3. Domed Electrode Leveling Tool, P/N 515-11835-001.
4. Gap Calibration Kit, P/N 857-10229-001 – 4400 and 4500 Systems.
Gap Calibration Kit, P/N 857-10229-002 – 4600 System.
This kit contains four tools. Each tool consists of a Gap Gauge Base and Plug.
5. Adjustable Nut Sleeve Tool, P/N 515-11116-001.
6. Vernier calipers calibrated in thousandths of an inch (or hundredths of a millimeter).
7. Screwdriver set.
8. Allen wrench set.
9. Flashlight.
Preparation:
Warning: Wear gloves and other appropriate solvent gear when working in the chamber. Do not breathe the chamber gasses.
1. Vent and open the process chamber. Refer to the appropriate automatic vent procedure.
2. On systems fitted with a clamp, remove the clamp before performing the parallelism part of this procedure. Refer to the appropriate Lower Clamp Removal procedure.
3. Also make sure the confinement ring and plunger attachment plate have been removed.
Procedure:
Section A Electrode Parallelism Testing and Adjustment:
1. Remove the lower electrode focus rings and filler ring if the system has one.
2. Place the dome electrode leveling tool on the lower electrode.
Note: At PCC, only one leveling tool is available. You can practice the parallelism procedure but not the Gap Spacing Calibration Procedure if you do not have this leveling tool.
3. Place the four gap calibration tools evenly on the domed electrode leveling tool in the following manner:
4400-4600 systems: place the tools in a 8.4” diameter circle.
4-6” 4500 systems: place the tools in a 6.4” diameter circle.
8” 4500 systems: place the tools in a 8.4” diameter circle (between the out most two circles).
For All systems, place the gauges on imaginary diagonal lines connecting two lead screws. As shown in the following figure:
If you do no have the leveling tool, place the outer edges of your gauges directly on top of the domed electrode, flush against the circle on top of the electrode as in the following figure.
NOTE: a) Be sure to push each gap gauge plug out to maximum extension beyond its base. B) Measure and record down the height of the gauges. C) Place the shortest gauge closest to your view port window. This way you can easily see if the upper electrode is touching down on all of the gauges later on in the procedure.
4. Close and latch the upper chamber assembly.
5. Select the Entrance Loadlock Macro page and command the inner door open.
Index 206 0 = Open
Index 207 1 = Open
NOTE: At this point, the door will not open due to the vented condition of the load lock. Manual override of the interlock is accomplished by manually operating the solenoid for the entrance load lock inner door. The solenoid is labeled SOV 23, Ent. Inner Door Open, 17J17. Press the orange button on the solenoid to manually open it.
6. Select the Chamber Macro page.
7. Move the cursor to Index 246 (GAP SETPT) and enter a value of 2.5 cm for 4500 systems if you are using the leveling tool. If you are not using the leveling tool, set distance to 1.9cm. (4600 Systems with Clamp, 4.0 cm).
Note: Anytime you lower the gap to <2.5 cm, you or your partner has to look through the view port window to ensure that the upper electrode does not collide into the black bases of the gap gauges.
8. Using a flashlight, look through the chamber window to determine if the upper electrode is in contact with the gap calibration tools.
9. If it is not, command the gap down by decreasing the gap set point in increments of approximately 0.2 cm until the electrode comes in contact with all four tools.
NOTE: It is important that the gap is in firm contact with all four gap tools. You know that for sure if you see the upper electrode compressing the shortest gauge a bit.
10. Select the Entrance Loadlock Macro page.
11. Move the cursor to Index 208 (ELL PUMP VALVE) and open the valve (1 = OPEN) to pump down the chamber.
12. When Index 0 (ELL VAC SENS) reads 1,000, select the Chamber Macro page.
Warning: In the next step THE GAP POSITION SHOULD NOT BE LESS THAN 1.6 CM FOR 4400 AND 4500 SYSTEMS AND 3.5 FOR 4600 SYSTEMS. If the gap is set lower than these limits, the upper electrode will collide with the gap gages and damage the electrodes.
Note: Systems at PCC very often require gap position < 1.6cm. But make sure it is still > 1.5cm. You have to ensure that the upper electrode does not collide into the black bases of the gap gauges by eye through the view port window. If you are not using the leveling tool, your gap should not go < 1.0cm.
13. Move the cursor to Index 246 and enter a value of 0.1 cm less than the current setpoint value. This will insure that with the decreased pressure the gap tools have been sufficiently compressed to obtain a measurement.
14. Record the present gap setpoint for future reference.
15. At Index 246, change the gap setpoint to 5.5 cm.
16. Select the Entrance Loadlock Macro page and close the loadlock pump valve (0 = CLOSE).
17. Move the cursor to Index 112 (ELL VENT VALVE) and open the valve (1 = OPEN).
18. When Index 61 (ELL ATM SENSE) reads TRUE, close the vent valve (0 = CLOSE).
19. Close the ELL inner door. Open the chamber.
20. For systems without a one piece gas line, install the chamber by-pass tube into the reactor gas line.
21. Remove the gap tools the chamber one at a time and measure their thickness the using vernier calipers. Record the position of the tool along with the measurement.
22. Evaluate the four measurements to determine if parallelism adjustments are required.
NOTE: A parallelism adjustment must be made if the measured difference between any two gap tools exceeds .002 inches (.005 cm).
23. If parallelism adjustment is not required, skip to the Completion section of this procedure.
24. If parallelism adjustment is required, the gap housing may be leveled by adjusting lowest corner of the upper chamber assembly. To achieve parallelism, follow steps 26 through 29 and refer to Figure A.
25. Locate the two 5-32 socket head screws on either side of the lead screw port of the lead screw that requires adjustment (see Figure A).
26. Loosen the screws. This will loosen the ball nut clamp.
Note: Loosen the screws 2~3 full turns. If you loosen it too much, the clamp at the back side of the screw will fall off. If you do not loosen it enough, the nut adjust sleeve will not turn smoothly.
27. Using the adjustable nut sleeve tool (LRC Part 515-11116-001), turn the nut adjust sleeve on the lead screw (see Figure A) counterclockwise to raise the lowest corner of the gap. One complete turn of the sleeve is approximately 0.76 cm = 0.3 inch. (1inch = 2.54cm). (rotation in degrees = Difference in inch*360/0.3inch)
28. Evenly re-tighten the socket head screws.
29. Repeat steps 3 through 29 as necessary until the upper and lower electrode are parallel (i.e. all four gap tool measurements are within 0.002 inches or 0.005 cm of one another).
NOTE: Remember to push each of the gap gage plugs out to maximum extension beyond their bases for each new measurement.
Section B. Gap Spacing Calibration
1. Calculate the average of the last four gap tool measurements plus 0.6 cm.
2. Compare the gap setpoint reference in Index246 obtained while doing gap parallelism to the average of the four gap tool measurements plus 0.6 cm.
If the measurement is greater than the setpoint, add the difference (multiplied by
1000) to the value displayed in the Gap Cal (256) field on the Chamber Macro
page.
If measurement is less than the setpoint, subtract the difference (multiplied by
1000) from the value displayed.
3. Repeat section A and recheck the gap spacing.
Sample Calculation
An imaginary reading for the gap setpoint value in step 10 of 1.180 cm and a gap
calibration value of 5610 is being used for illustration purposes.
Compare gap setpoint to gap tool measurement:
gap tool measurement = 1.182 cm
step 10, GAP CAL (256) reading = -1.180 cm
compared difference = 0.002 cm
Calibrate the gap:
If the gap tool measurement is greater than the setpoint reading in step 10, add
the compared difference to gap calibration field:
GAP CAL (256) = 5610
difference 0.002 x 1000 = + 2
gap calibration result = 5612
Entered result GAP CAL (256) = 5612
If the gap tool measurement is less than the setpoint reading in step 10, subtract
the compared difference from gap calibration field:
GAP CAL (256) = 5610
difference 0.002 x 1000 = - 2
gap calibration result = 5608
Entered result to GAP CAL (256) = 5608
Completion:
1. Remove the domed tools from the lower electrode.
2. Re-install the lower focus ring.
3. Re-install the filler ring.
4. Perform the Replacement portion of the applicable Plunger Attachment Plate Removal Procedure.
5. Perform the Completion section of the Confinement Ring Change Procedure
6. Perform the Completion portion of the applicable Chamber Automatic Vent Procedure.
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