CCT System Operation & Monitoring 4

Question 1

During Casper system operation, the process recipe calls for a pressure ramp from 5 mTorr to 50 mTorr over 30 seconds. The throttle valve controller fails to track. What is the MOST likely result if the process continues?

Accepted Answer

Process deviation leading to out-of-spec results and possible wafer damage

Answer

Uncontrolled pressure deviations alter plasma density and etch chemistry, leading to out-of-spec process results and potential wafer damage.

Question 2

A Casper system's remote I/O module stops communicating during a run. Which system function is MOST at risk of uncontrolled behavior?

Accepted Answer

Digital valve states and interlock feedback signals

Answer

Remote I/O modules control digital valve outputs and read interlock inputs; loss of communication can leave valves in undefined states and disable safety feedback.

Question 3

When comparing Casper system idle base pressure to the qualification baseline, a 40% increase is observed. The FIRST diagnostic step should be:

Accepted Answer

Perform a residual gas analysis (RGA) scan to identify contamination sources

Answer

An RGA scan identifies which gas species are elevated, distinguishing between leaks (atmospheric gases) and outgassing (water vapor, process residues).

Question 4

A Casper system operator reports that wafer temperature uniformity has degraded from ±2°C to ±8°C across the wafer. Which component is MOST likely responsible?

Accepted Answer

ESC zone-to-zone helium backside pressure imbalance

Answer

Helium backside gas pressure on the ESC controls wafer-to-chuck heat transfer; imbalance between zones causes non-uniform wafer temperature.

Question 5

In a Casper monitoring system, OES (Optical Emission Spectroscopy) data shows a sudden increase in the Si emission line intensity mid-process. This MOST likely indicates:

Accepted Answer

A process endpoint has been reached and silicon is being exposed

Answer

A rising Si emission signal during etch typically signals that the underlying silicon layer is being exposed, often used as an end-point detection signal.

(CCT) Certified Casper Technician Practice Test

(CCT) Certified Casper Technician Practice Test

CCT System Operation & Monitoring 4