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AUTOMATIC ENDPOINT DETECTORS

AUTOMATIC ENDPOINT DETECTORS FOR DEPOSITION AND ETCHING SYSTEMS

Endpoint detectors (EPD) are an important tool for achieving optimal process results. The use of an EPD ensures processes are carefully controlled and consistent, to ensure reliable repeatable results are achieved wafer-after-wafer, batch-to-batch. Several techniques exist and it is vitally important to understand the strengths of each and how they fit with your process requirements to achieve what you need. Upgrade now and receive multiple benefits.

We supply a wide range of endpoint detector upgrades under these two categories:

  • Optical Emission Spectroscopy (OES)
  • Laser interferometry
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Horiba LEM Endpoint

Optical Emission Spectroscopy (OES)


Options Ocean Insight USB4000 AvaSpec - Mini2048CL  Verity SD1024G Verity SD1024GH Horiba EV 2.0
Wavelength range 200 - 850 nm 200 - 1100 nm 200 - 800 nm 200 - 800 nm 200 - 1050 nm
Spectrometer Real time Real time Real time Real time Real time
Endpoint Yes Yes Advanced algorithms Advanced algorithms Advanced algorithms
Chamber condition analysis Yes Yes Yes Yes Yes
Etch process monitor Yes Yes Yes Yes Yes
Reprocess No No Yes Yes Yes
Resolution Good for general single layer process Good for general single layer process Excellent for complex multilayer Superior for complex multilayer Good for complex multilayer
Suitable for PECVD, RIE, ICP-RIE, CVD and ALD Systems PECVD, RIE, ICP-RIE, CVD and ALD Systems RIE and ICP-RIE Systems RIE and ICP-RIE Systems RIE and ICP-RIE Systems
Example Applications PECVD chamber clean, SiO2/SiNx etch, PR strip, general purpose etching PECVD chamber clean, SiO2/SiNx etch, PR strip, general purpose etching SiO2/SiNx etch, GaAs/ AlGaAs/ GaSb/ AlGaSb, InP/ InGaAs/ InGaAsP/ InAlGaAs, Metals, Plasma analysis SiO2/SiNx etch, GaAs/ AlGaAs/ GaSb/ AlGaSb, InP/ InGaAs/ InGaAsP/ InAlGaAs, Metals, Plasma analysis, Deep Si, GaAs VCSEL GaAs/ AlGaAs/ GaSb/ AlGaSb, InP/ InGaAs/ InGaAsP/ InAlGaAs, PR Strip, Plasma analysis

Optical emission spectroscopy (OES) monitors the light emitted by the plasma. Measuring the intensity of light emitted at a specific wavelength in a spectrum allows a relative measurement of the concentration of a given species.

Etch by-products and gas species have characteristic emission wavelengths, so process endpoints can be detected by looking for changes in these emissions as the etch reaches a new layer. OES endpointing typically requires an etched area of several cm2 to provide a detectable concentration of etched species in the plasma, depending also on etch rate and plasma emission intensity.

A popular application of OES is in the plasma cleaning of PECVD chambers. Measurement of the fluorine emission intensity is used to determine the endpoint of chamber plasma cleaning. During cleaning the fluorine concentration will be low as it is being consumed by the etching process, but it will rise sharply when the chamber walls become clean, providing an endpoint.

Typical endpoint units for PECVD chamber clean endpointing are as follows:

  • Ocean Insight USB4000 spectrometer kit (200-850 nm spectrometer). The full spectrum capability additionally allows chamber and process monitoring, e.g. by comparison of current spectra with a reference to aid with process troubleshooting.
  • AvaSpec-Mini2048CL with a wider wavelength range.

Benefits of OES endpoint detector upgrade

  • Allows a precise stop on a particular layer, improving throughput and yield
  • Improve process reproducibility
  • Reduced cost of ownership
  • Reduced particulate generation by preventing over-cleaning, leading to improved process yield
  • Extended life of chamber components due to less over-cleaning
  • Enables monitoring of chamber condition and process ‘health’ in real time
Optical Emission Intensity Optical Emission Spectroscopy end pointing

Laser Interferometry

Options Horiba LEM Intellemetrics LEP500
Movement XY and tilt adjustment XY and tilt adjustment
Sample image magnification x50 x50
Laser wavelength 670/ 905 nm 670/ 980 nm
Laser spot size 30 to 60μm  8 to 24μm
Layer structure modelling No Yes
Suitable for RIE and ICP-RIE Systems RIE and ICP-RIE Systems
Example Applications SiO2/ SiNx, Metals, GaAs/ AlGaAs/ GaSb/ AlGaSb, PR strip, Failure Analysis Metals, GaAs VCSEL, GaAs/ AlGaAs/ GaSb/ AlGaSb, InP/ InGaAs/ InGaAsP/ InAlGaAs, PR strip

A laser interferometer measures the change in reflectance of the wafer surface during etching or deposition, by focussing a laser spot onto the wafer and measuring the intensity of the reflected laser light. The laser interferometer camera also provides a TV image of the wafer surface to allow precise positioning of the laser spot onto the correct region.

The etch rate can be calculated by monitoring ripples in the laser signal due to interference effects within the thin film, allowing the etch to be stopped at a certain depth within the layer. Interfaces between layers can also be detected, as this typically results in an abrupt change in reflectance.

Laser interferometry typically requires user intervention to position the spot before each run (unless a specific region of the wafer is dedicated for laser endpointing).

Benefits of Laser endpoint detector upgrade

  • Enables etch depth monitoring and endpointing
  • Allows ‘etch-to-depth’ within a layer
  • Precise etch depth control within multi-layer structures
  • Allows endpointing on small samples or those that do not provide a strong OES endpoint
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