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Material Deposition and Device Fabrication in the Silicon Cluster Tool

This page provides additional details on materials deposition and device fabrication using the Silicon cluster tool.

Very High Frequency (VHF) Plasma-Enhanced Chemical Vapor Deposition (PECVD) Chamber

Photo of a square metal chamber with a larger metal flange on the top.  A small metal box is attached on the right side of the main chamber, and a white heating cable goes from the top of this box to inside the large flange. The unit is labeled with a sign that says "VHF PECVD." The top of the silicon cluster tool is seen in the background.

Very-high-frequency plasma-enhanced chemical vapor deposition tool, attached to the Silicon cluster tool.

Deposition at high frequencies enables short deposition times and high deposition rates, and both are needed to produce high-quality microcrystalline silicon layers in an industrial setting. This VHF PECVD chamber contributes to the Silicon cluster tool's ability to study the effects on solar cell performance of frequency, substrate temperature, and pressure.

Applications:

  • Depositing intrinsic a-Si:H and µc-Si:H layers

Specific features:

  • Substrate temperature up to 400°C
  • Variable frequencies up to 100 MHz
  • Base pressure ~10-8 torr (ultra-high vacuum)
  • Process pressures up to 1 torr
  • Gas flow rates from 0 to 500 sccm
  • Flow gases are SiH4, H2, Ar, and SiD4

Combinatorial Plasma-Enhanced Chemical Vapor Deposition (Combi-PECVD) Chambers: p-Type and i-Type Layers

These combinatorial chambers allow researchers to vary the temperature and thicknesses of p- and i-type layers within a single sample. By allowing this range of deposition parameters, this tool greatly enhances the efficiency of the analysis capabilities for silicon wafers.

Photo of a cylindrical metal chamber with a large metal flange on the top and on one side.  Several small viewing ports are also visible.  A black box-like manipulator unit sits on top of the cylinder and has black hoses entering into a flange on the the top. The unit is labeled with a sign that says "Combi PECVD." The top of the Silicon cluster tool is seen in the background.

Combinatorial plasma-enhanced chemical vapor deposition tool, attached to the Silicon cluster tool.

Applications:

  • i-layer chamber: depositing intrinsic a-Si:H layers
  • p-layer chamber: depositing p-type layers doped with BF3, B2H6, or trimethylboron (TMB)

Specific features:

  • Uniform substrate temperature to 400°C
  • Temperature can be graded from 300° to 700°C across a 157-mm substrate
  • Base pressures ~10-8 torr (ultra-high vacuum)
  • Process pressures up to 1 torr
  • PECVD performed at 13.56 MHz
  • Gas flow rates from 0 to 500 sccm
  • Flow gases:
    • i-layer chamber: SiH4, H2, GeH4, and Ar
    • p-layer chamber: Ar, TMB/SiH4, BF3/He, TMB/He, H2, CH4, SiH4, and B2H6/H2

Plasma-Enhanced Chemical Vapor Deposition (PECVD) Chambers: n-Type and SiNx Layers

These two PECVD chambers allow researchers to deposit n-type a-Si:H and SiNx layers and also allow in situ optical measurements.

Photo of a square metal chamber with a larger metal flange on the top, a viewing port on the front, and a large-diameter metal elbow on the left. A small metal box is attached on the right side of the main chamber and is marked with a yellow and black sign that says "Caution Hot Surface, Do Not Touch."  Two white heater cables go from the side of this box to inside the large flange. The unit is labeled with a sign that says "PECVD SiNx." The top of the Silicon cluster tool is seen in the background.

Plasma-enhanced chemical vapor tool for depositing silicon nitride as an antireflection layer.

Applications:

  • SiNx chamber: depositing SiNx layers
  • n-type chamber: depositing n-type a-Si:H layers; PH3 doping

Specific features:

  • Operating frequency is 13.56 MHz
  • Substrate temperature up to 400°C with uniformity ±12°C
  • Base pressure ~10-8 torr (ultra-high vacuum)
  • Process pressures up to 1 torr
  • Gas flow rates from 0 to 500 sccm
  • Thickness uniformity ±10%
  • In-situ ellipsometry ports
  • Deposition rate ~1 Å/s
  • Flow gases:
    • SiNx chamber: SiH4, NH3, N2, N20, H2, Ar
    • n-type layer: SiH4, PH3/H2, PH3/SiH4, Ar, H2

Combinatorial Hot-Wire Chemical Vapor Deposition (Combi-HWCVD) Chamber

The combinatorial HWCVD chamber allows researchers to deposit a-Si:H layers using various hot-wire configurations, giving advanced diagnostic and characterization techniques.

Photo of a man in a blue shirt who is looking at a metal chamber that has a circular viewing port in the front that shows an orange glow from hot-wire filaments within.  The chamber is connected to a cylindrical cluster tool partially seen in the background.

Researcher operating the Silicon cluster tool in the Process Development and Integration Laboratory.

Applications:

  • Depositing intrinsic silicon layers (a-Si:H, a-SiGe:H, a-SiNx)
  • Studying the effects of flow rate, frequency, and substrate temperature on layer quality

Specific features:

  • Ammonia nitrogen source
  • Typical substrate-to-filament distance is 5 cm, adjustable to within ±2.5 cm
  • Gas flow rates from 0 to 200 sccm (depending on the gas)
  • Face-down sample orientation
  • Temperatures up to 700°C
  • Temperature grading from 300° to 700°C across a 157-mm substrate
  • Filaments are graphite or tungsten
  • Capability for combinatorial techniques

Transparent Conducting Oxide (TCO) Sputtering Chamber

Photo of rectangular metal chamber sitting on top of a metal frame or rack holding other related equipment. The chamber has three small flanges on the side, and the entire unit is connected to a cylidrical cluster tool to the left. Emergency power off buttons are visible along the right edge of the rack.

Sputtering tool, attached to the Silicon cluster tool in the Process Development and Integration Laboratory.

This radio-frequency sputtering chamber allows researchers to vary the TCO composition and to determine effects of deposition parameters. If desired, the targets—as well as the entire chamber—can be exchanged for alternatives provided by collaborating researchers.

Applications:

  • Depositing and researching TCO layers

Specific features:

  • Substrate temperature up to 400°C
  • Surface thickness uniformity expected is ~10%
  • Typical layer thickness is 100 nm (for ZnO, it could be up to 1 µm)
  • Face-down sample orientation
  • Cathode-to-substrate distance is 5 cm
  • Two targets (ITO, ZnO), with room for a third target
  • Power source is radio frequency
  • Base pressure ~10-8 torr

For more information, contact Qi Wang.