Why Spare Parts Management for Plasma
- Any part in contact with the plasma impacts the
- Spare parts are a major cost driver.
- So often second-source parts are used
– with sometimes different properties !
- The process stability depends in particular on
- Surface temperature if not well controlled
- Chemical surface conditions, in particular in case
of memory effects
- In particular if regularly cleaning during PM
Spare parts management
- Qualification and characterization of second source
- Tracking and monitoring of age and cleaning cycles of
- Product wafers → Message
comes usually too late.
- Test wafers
→ Necessary but not sufficient, not very
Low Pressure Process Example
etching of dielectric with low damage
pressure 0.7 Pa (5 mTorr)
bias power, due to low pressure no collision in sheath
- → Low
but well defined ion energy keeps etch rate high but minimizes risk of
impact: Ceramic chamber wall changes during PM
- The most sensitive
tool parameters - RF peak voltages
at and does not respond to spare part changes and
rate is in this low pressure regime only sensitive to
adaptation – due to stochastic heating of electrons.
different ceramic parts – same level in plasma
- One Second source ceramic - lower level.
density is also but less affected fits to products
still in spec.
- Isotropic etching with low damage, surface
preparation and descum
- Low pressure 11 Pa (80 mTorr)
- Very low bias power
→ Mainly chemical (O)
etching with very low ion energy.
- Vp from coil shows
only a slight RF
please compare RF power in diagram below.
- In both RF peak voltages no response to spare part
still shows the known, 'ceramic' pattern
- Only weak pattern in plasma density.
- RF Power adjustment not seen here.
- … electron collision rate
indicates impact of gas temperature – due to ohmic heating of
- Accommodation coefficient and so gas cooling at
chamber wall depends
strongly on surface conditions.
pressure adaption shown only through
- Process adaptation for etch rate and
selectivity is best reflected in plasma parameters.
- The effects of ceramic chamber wall as spare part
- is well pronounced in plasma parameters and
- depends on process, mainly the pressure.
- Potential reasons for impact of ceramic chamber wall:
- Variations in heat flow from gas to chamber wall
- Different permittivity of the ceramics.
- Smart spare part management can be controlled by
provided by model-based sensors.
- You are also welcome to contact our Services
Team to get additional information.