HERCULES^® - FAQs 

Hercules^®: Plasma Metrology System - Sensor Head - Data Management - Software

Hercules®:Plasma Metrology System
Can Hercules collect data from 6 chambers of 3 Dry Etch tools for instance?	Yes it can if there is a proper data collection system (as Maestria). But one needs six Hercules® systems if one wants to do it simultaneously.
Does AC 100 V power can drive Hercules®?	No problem at all. This is the most common case since often the power line of the tool is used.
Is there a possibility to use it for DC magnetron sputtering?	No, DC does not provide th effect which is utilized by SEERS.
I want to know measurable pressure range under the conditions that gasses and RF power can be fixed.	This depends on RF power and the gases used. The spec says up to 35 Pa  (250 mTorr). This is very conservative, often (e.g., O2) it works also at 50 Pa (350 mTorr).
I want to know which application were done by SEERS and which application were done by NEED.	NEED is brand new und the high-pressure approach for more than 60 Pa (0.5 Torr) and basically specially made for PECVD. Almost all etch application will use SEERS also in future.
Is it possible to do measurement through Quartz furnace wall that have the thickness about 5 to 15 mm? What is the maximum thickness of the furnace wall that the measurement can be carried out?	If that is quartz liner which covers the whole chamber wall, it will work independent of the thickness of the quartz liner. Hercules® measures at some SCCM chamber through a ceramics liner. 15 mm are still fine, much more would be tricky and must be discussed in connection with the chamber design.
Could you explain how the nonlinearity of the plasma is related to frequency domain in the simplified model of RF plasma?	The nonlinearity of the sheath (dark space) at the wafer generaties the harmonics. Example for the simple term [x(t)]2 in the RF sheath equation: The Fourier transform provides X*X (convolution) and its frequency shift rule show the occurance of a new harmonic frequency (multiple of basic frequency). A simple is cos2 (2 π f t) = 0.5 [1 + cos (2 π f t)] where the square term provides a signal with double generator frequency 2 π f .
What is the difference between VI probe and the plasma metrology system Hercules®?	A VI probe delivers voltage V, RF current I, and the phase angle φ between V and I outside the chamber. From this data one can calculate resistance using an simple eqivalent circuit with series circuit of capacitance C and resistance R. A VI probe delivers NO plasma parameters, just parameters from somewhere outside the chamber. That means FDC for the RF subsystem YES, process control NO. In contrast to the VI probe, Hercules® measures and uses the full RF spectrum (up to 1 GHz) is a model-based sensor system with a real plasma model including nonlinear effects.

Sensor Head
Is there an instruction for sensor installation and sensor mounting position?	Yes, please find the installation guidelines in the sensor catalogue.
The availability of universal sensor, do you have any universal sensor for a common flange types? Some users want to minimize the number of the sensors to be tested to different chamber for evaluation purpose regardless of cross contamination.	Due to the large differences in flange diameters and flange types used and the 50 Ohm geometry this is very difficult. That goal can only be achieved in cooperation with the the tool suppliers for special chambers.
Want to know the specifications of the cable to be connected the sensor?	The cable model is RG 223 U-01. This is a special low damping cable with very low tolerance of the cable parameters and special SMA connectors (some metal combinations are unreasonable in semiconductor manufacturing). These cable are specially made for Plasmetrex by one of the biggest RF cable providers. Plasmetrex strongly recommend to use only these cables to maintain accuracy and reliability.
We understand that even non-conductor (like a polymer) stick upon sensor, there is no influence to detect RF current, is it right? How about if conductor (like a Al) stick upon sensor, is there any influence or changing to detect RF current? What will be happen?	For etching application no problem, also if there was some metal at the chamber wall. For sputtering: If the resistance of the metal laxer at the sensor head gets very low (<< 50 Ohms), the signal magnitude decreases. This is basically no problem if the signal is well above the threshold which is given by the digitizer. To reduces that effect, we have special sensors for sputter chambers (not in the sensor data base)

Data Management
Do you have any guide line of data size?	For the order of magnitude we can set to 100 kB per lot. If we assume 10 lots per day, we have 400 MB per year. Usually provide 120 GB hard disk. Should be no issue. This is one of the great feature of Hercules®. They are already compressed by real model with a great compression ratio.
When we don't integrate with FDC, use Master only, how we can detect 1 wafer from RF signal?	Also in case Hercules® works with Maestria, it detects the plasma independently and starts data collection. If there is no fab-wide FDC system Plasmetrex SAPC Server for the conrol of tool and sensor data can be used.
How can we know start / stop for 1 Wafer during data collection period?	But it provides "0" if it is ask via the interface.

Software
What is the difference of HercView and HercLotView? Does HercLotView show 1 dot as 1 wafer?	HercView is suited for the detailed analysis of one lot and HercLotView in particular for long term analysis and chamber matching. HercLotView shows 1 dot as 1 wafer, but the HercLotView can also show the time curves by snap shot feature.

 Please contact us if you have any various questions more.