PlasmaPro System100 PECVD

Transfer station (square or hexagonal)

Vacuum cassette(s)

Inductive Coupled Plasma Sources with ESS

Wide temperature range substrate

Laser interferometry /optical emission

Inductive Coupled Plasma Sources with ESS

Electrostatic Screen for ICP

“ICP Sources” without the Electrostatic Screen (ESS) have a strong capacitive coupling component leading to:

* increased wall sputtering (contamination on the wafer, decreased wall lifetime/ implosions)
* increased ion bombardment on the wafer (increased ion induced damage)
* possibility of generator “cross talking” (instable plasma)

Wide temperature range substrate electrode:-150° C – +400° C, RF driven

Laser interferometry /optical emission-> show load sequence

Laser Interferometry

The “single beam” laser interferometer is recommended for in situ rate/ depth measurements.
It is often used in the “reflectance mode”, where we just monitor changes in the surface reflection.
It can also be used in the “interferometric mode” , where interference signals from two interfaces (e.g. the top of a transparent layer and its bottom or the bottom of an etch and the coated substrate backside).

In-situ etch rate monitoring
Endpoint does not require etch stop layer
Endpoint can be chosen anywhere within the layer once etch rate has been established.

675 nm is the standard wavelength for laser interferometry.
However, for certain III-V applications, e.g. InP-related materials, 905 nm is often more suitable, since the index contrast between InP-related materials is greater (and absorption is lower) at 905nm.
A 905 nm laser endpoint system with high gain amplification of endpoint signal is available from OPT for these demanding endpoint applications.
For GaAs VCSEL DBR stack etching, it is common to use a 675 nm laser interferometer, since this gives
a clearer endpoint trace, typically with each ‚ripple’ relating to each layer within the structure.
For thicker GaAs layers (> about 0.5 microns of GaAs film thickness) 905 nm is typically recommended, since absorption of the laser light is much lower at this wavelength.
Laser endpoint traces can be modelled by OPT for any stack of materials, allowing optimum choice of laser wavelength for any given endpoint requirement.

Optical Emission

Monitoring of reactive species or etch by-products provides endpoint signal.

Endpoint relies on etch stop layer.

Scanned monochromator allows full spectrum analysis.

Trace achieved when etching SiOx layers down to a Si substrate.

It shows a typical trace obtained when etching SiOx layers down to a Si substrate. The large picture shows the full emission spectra of the plasma. The blue and red marker lines correspond to the emission peaks of CO, which is an SiOx etch by-product, at 483 nm and 520 nm.
The small graph in the top right hand corner shows the fall in the intensity of these CO etch by-product emission peaks, as the last SiOx is removed. By monitoring the time derivative of this CO emission intensity it is possible to obtain a very reliable endpoint trigger.

Substrate Transfer

Plasmalab System 100:

Wafer/ Substrate transfer

with “Helium Backside Cooling”