With the new development and unmatched technology of XPL-900 High rate dry etcher system, Secon is ready to provide an ideal solution in thinning the wafer up to customer requirement. However, thin handling always an important issue that need full attention in transportation of thin wafer before and after etching.

Secon uses electrostatic technique in handling thin wafer at the following two condition: -

• Wafer clamping by Electrostatic Chuck (ESC) during etch process 
• Wafer transferring by electrostatic End piece between the process chamber and load/unload cassettes

Principle of ESC Clamping

The wafer is hold by electrostatic forces: DC-power induces in two electrodes different loading (+ve and -ve). As there is no galvanic contact between the electrodes, no current can pass through the ESC nor through the wafer. There is only a loading of the wafer opposite to the electrodes. These electrostatic process was approved create NO HARM to the wafer itself by the monitoring CHARM-2 wafer from the WCM (Wafer Charging Monitors, USA). This CHARM-2 wafer provides several important ability to detect and measure the voltage level, current induced and UV effect on the wafer.

The border of the ESC is slightly higher that the rest of the ESC structure. Therefore the helium leakage is a minimum. The border and the helium leakage work like a barrier against any introduction of radicals and ions under the wafer.

The helium leakage is also used as an indicator for the clamping force of the ESC. If the leakage is too high, the wafer is not correctly deposited on the ESC chuck and the XPL-900 system will not start the process.

Key Benefits

The helium gas flow provide the following advantages: -

• Gas leakage indicator of the clamping force of the ESC chuck
• Assist in de-chucking wafer the etch process by a purge He gas
• Cooling purpose during the etching process, thus the temperature is well control below 100 ºC
• No plasma etching on the active layer of wafer without frontside protection

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Thin Wafer Handling

There are several wafer handling used in the operation of semiconductor industry. For example, wafer fork handler, vacuum handler or Bernoulli (Contactless) technique. Secon use the electrostatic end piece to handle the thin wafer under the vacuum condition. The electrostatic end piece (ESC End piece) work perfectly under the vacuum condition and capable to handle wafer less than 50 µm. It is also proven by the monitoring CHARM-2 wafer, that no negative impact induced to the wafer after handling by the electrostatic end piece.

The backside of the wafer will be contacted to the ESC End piece, then it will be transferred to the etching module and place on the ESC chuck. After etching processing, the ESC End piece will dechuck the wafer from the ESC chuck, the Helium gas purge will push the wafer to the ESC End piece. After dechucking, ESC End piece will transfer the wafer return to the unloading station (magazine or jarpack). The ESC End piece is capable to handle a piece of paper from paper dispenser as the separator between processed wafer in a jarpack. 

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Last modified: Oktober 28, 2004