Specific Process Knowledge/Etch/DRIE-Pegasus/picoscope

Feedback to this page: click here

Process optimization using the Picoscope

Before going into details on why it makes sense to optimize the processes using the picoscope process monitoring, we need to have a look at how this is usually done.

Standard process parameter monitoring

The original standard recipes on Pegasus 1 differ in many ways. The second step of one of them is listed below:

Process A Step 2 parameters
Parameter	Etch	Dep
Gas flow (sccm)	SF6 350 (1.5 s), 550	C4F8 200
Cycle time (secs)	7.0	4.0
Pressure (mtorr)	25 (1.5 s), 150	25
Coil power (W)	2800	2000
Platen power (W)	140 (1.5) 45	0
Common	Temperature 20 degs

When running any recipe on the SPTS Pro software, a set of process parameters are recorded as the process runs. This data can be accessed later by looking up the datalog. Which parameters are recorded is dictated by the socalled logging recipe that is selected for every process recipe. The list of possible parameters to include in a logging recipe is long and is comprised of both input parameters such as 'Coil forward power demand' and 'SF₆ flow setpoint', and measured values such as 'Platen temperature' and 'Platen DC Bias'. During the process itself, one can also activate the 'Trace' to monitor the process parameters in real time.

To the left in the figure below, some of the most important process parameters are shown for a process run of the recipe Process A.

• 4 cycles of Process A
• 
  Left: Recorded with the SPTS software
• 
  Right: Recorded with the Picoscope

One can see the multiplexing of the Bosch process by alternation of the gas flows of SF₆ and C₄F₈

• 4 cycles of Process D4
• 
  Left: Recorded with the SPTS software
• 
  Right: Recorded with the Picoscope

4 cycles of the recipe PrD4 recorded with the Picoscope

4 cycles of the recipe PrD4 recorded with the SPTS software

4 cycles of the recipe Prcocess A recorded with the Picoscope

4 cycles of the recipe PrD4 recorded with the SPTS software