The dedicated Electro-Static Chuck (ESC) Watchdog
The Electro-Static Chuck ESC Guardian
With the move from 150mm to 200mm and 300mm wafers, the wafer mechanical clamps in plasma processes became obsolete, while the new generation of Electro-Static Chucks (‘ESC’) became the state-of-the-art in wafer clamping.
The high power of the plasma and the need for uniform wafer temperature made the backside Helium cooling system a most critical issue, that has significant affect on capacity, yields and scrap.
The thermodynamic properties of the chuck and its surface, the backside helium pressure (inner and outer), the electrostatic force and the closed-loop cooling system comprise a complex system that must be carefully controlled and maintained in order to keep the process qualities within the required boundaries.
Although most machines have acceptable level of chuck control, enhanced insitu monitoring and analysis enables to increase qualities at an easy to justify ROI.
Tadin developed the ESC Guardian as a special watchdog for the Helium assisted ESC clamping and cooling system.
The ESC Guardian monitors the critical ESC parameters and continuously performs a set of real-time tests to ensure proper operation of the system by predicting and informing on any deviation. In addition, the ESC Guardian logs the operation parameters thereby enabling to analyze historical behavior and optimize operation by better setup.
The ESC Guardian comes in two formats: As a one per chuck enclosed box computer with no built-in user interface, and as a full-featured mini-computer, with built-in display and keyboard.
The ESC Guardian connects to the chuck using specially designed piggy-back connectors for most known machine configurations. The net installation time does not normally exceed one hour per chamber.
The Guardian can be connected to the network for remote access, and it can also perform in stand-alone mode, enabling to halt the machine operation if out-of-spec condition is predicted per each wafer.
The monitored parameters
In normal ESC Guardian configuration, the following parameters are monitored and analyzed:
1. Backside Helium pressure – Inner (Center)
2. Backside Helium flow – Inner (Center)
2. Backside Helium pressure – Outer (Edge)
3. Backside Helium flow – Outer (Edge)
4. ESC Voltage
5. ESC Current
6. Cooling agent temperature (optional)
7. Wafer temperature (optional)
8. Vent vacuum (optional)
9. Final valve (on/off) – Inner
10. Final valve (on/off) – Outer
11. Helium valve – Inner
12. Helium valve – Outer
13. Slit valve (optional)
14. Vacuum valve (optional)
15. Wafer pins (optional)
For process tracking (recipe, lot#, wafer#), the ESC Guardian can be connected inline to the machine SECS using Tadin’s SecSpy(TM). When SecSpy is used, the Guardian internal database will include the work information, enabling correlation and tracking for historical analysis.
Remote access and data analysis
A special software package enables to remotely access the ESC Guardian, display all parameters in real-time and history, analyze the data and export the data to other database.
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