AGS - Service Notes

Service Note No: 13
To: RIE/CVD maintenance technicians
Subject: RF plasma or tuning problems with ATX600 match networks

Problem: The plasma is failing to ignite and/or you are seeing high reflected power readings. Nothing seems to help. A capacitor may be fixed to a certain position.

Solution: Isolate the problem. Most RF match problems are field repairable. Use the following guide to assist you. The past causes, in order of frequency seen, have been as follows:

1. Accidental button change: Power off, Auto to Manual, Preset jammed, etc.
2. Internal short circuit at electrode. Debris, deposits, or low water resistivity is shorting RF to ground
3. Loose control cable from front panel to network
4. Internal heat damage to drive belts
5. Failure of drive transistors on control board (attached to the bottom of network)
6. Shorted main RF strap to electrode feedthrough
7. Internal fixed capacitor failure (shunt, or "padder" caps)
8. New plasma settings not in range of network

Procedure: In any case, if the problem is not a simple button out of place, use this guide to troubleshoot:

1. Turn off RF power supply and open network access cover, inspect inside of network for obvious damage of failed components.
2. Push Auto button out (manual mode), try to change the capacitor settings with front panel controls and observe the variable capacitors. Are the motors turning? Are the capacitors position readings in agreement with the actual positions? If the capacitors turn in manual mode there is probably no problem with the network. Go to 3A. If either of the capacitors don't move go to 3B.
3. A. System RF problem: Disconnect the main RF strap. Check the resistance of the electrode with respect to ground. It must be greater than 500k Ohms. If not, replace the cooling water with high resistivity type and/or remove the electrodes and clean.
   B. Network problem: Disconnect the main RF strap. Disconnect the interconnect cables. Remove the match from the RF interconnect box and pull away from the system. Carefully remove the drive electronics access cover. inspect the unit for damaged components or loose parts. On older units, there was a problem with the drive transistors overheating and actually melting the solder and falling out of the PC board. Simply solder the transistor back into place and install TO-220 insulated heat sink kits to prevent future occurrences (contact A.G.Services for kit ordering information). Test manual operation. If the problem is burnt or melted components (belts, mounts, padder caps), replace bad parts, test manual operation (contact A.G.Services or Advanced Energy for ordering information).
4. For RIE systems, drill several 1/8 inch holes 1/2 inch apart from each other in a row across the top of the network to improve convection cooling. The proper location for the holes is on the right side, above the motors, about 1/2 inch from the top of the network box. It has been found that this fix sufficiently cools the network in high powered RIE applications.
5. When the repair is complete, reinstall and run the standard plasma test and keep a record of the results.

Preventive maintenance: Wet clean system weekly, Check RF system with standard plasma test monthly, Inspect RF components quarterly, Remove electrodes and clean both sides semi-annually, Replace closed-loop cooling water annually.

Note: Contact Advanced Energy Industries for additional assistance.

Expert Tips: You may obtain better etch rate repeatability by controlling the DC Bias. With the RFX600/ATX600 combination, power regulation can be selected in either forward power or DC Bias modes.

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