Silicon nitride

Silicon nitride, Si3N4, is a common dielectric material used in semi-conductor processing. It can be deposited on a wide variety of substrates using techniques such as LPCVD, PECVD, Sputtering, and Evaporation.

The deposition technique used will affect the quality and dielectric strength of the silicon nitride. Generally the higher the process temperature the higher the quality.

Silicon nitride is not always stoiometric, Si3N4. Low stress silicon nitride, (LS Silicon nitride) is silicon rich and the composition of PVD and PECVD silicon nitrde can vary depending on what stress or optical properties are desired in the final film.

Contents

Equipment

Process technologies that can be used to deposit/pattern this material. If this is a substrate, refer to what tool/process restrictions there may be and possibly remove the following sub-sections.

Deposition Equipment

• Low temperature deposition
  • Lab 18-1
  • PVD 75
• Medium temperature deposition
  • P5000 PECVD
  • GSI PECVD
  • Plasmatherm 790
• High temperature deposition
  • Tempress S2T2 - Nitride-HTO 6"
  • Tempress S2T3 - Nitride-HTO-OxyNitride 4"
  • Tempress S2T4 - Low Stress Nitride 4"

Etching Equipment

• Wet Etching
  • Acid Bench 02
• RIE Etching
  • P5000 RIE
  • LAM 9400
  • STS APS DGRIE
  • Plasmatherm 790

Characterization Equipment

• Material Properties
  • Woollam M-2000 Ellipsometer
  • NanoSpec 6100
  • Flexus 2320-S
  • Rame-Hart Goniometer.

Applications

• Dielectric
• Structural Layer
• LPCVD nitride can be used as a mask for KOH etching

Processes

Deposition Processes

• At the LNF there are multiple ways of depositing an Silicon Dioxide film. The processes are listed from highest to lowest temperature. This generally relates to film quality.
• Low-Pressure Chemical Vapor Deposition (LPCVD)
• Plasma Enhanced Chemical Vapor Deposition (PECVD)
  • Film quality will vary depending on the tool and the recipe selected.
  • Pinholes are common in PECVD films. Consult individual recipes for minimum thickness required to avoid pinholes.
• Sputter deposition
  • Deposition rates will be very slow.
  • High probability of pin holes.

Etching Processes

• Silicon Nitride is usually patterned using an etching process. The LNF has wet and dry etching capabilities.
• Wet etching*
  • LPCVD Silicon Nitride can be etched with Hot Phosphoric acid (Hot Phos) based solutions.
  • Low stress silicon nitride will etch slower in Hot Phosphoric Acid.

• RIE Etch*
  • Tool material restriction must be considered when selecting an RIE tool as it will impact what tools you can use for future process steps.
  • RIE is the easiest way to etch Silicon Nitrdie.
  • Most Silicon Nitride recipes have low selectivity to Silicon Oxide.

Characterization Processes

• Optical
  • The optical properties of the tool will vary depending on the deposition method used.
  • The optical techniques can be used to find the thickness of the film.
  • Elipsomentry can be used to find the n and k values.
• Stress
  • The Flexus 2320-S can be used to find the stress of the film.
  • Curvature of the wafer must be measured before deposition.
  • If film is deposited on both sides it must be removed from the backside before the second measurement is taken.
  • When measuring the initial curvature of the wafer you should use both wavelengths at the same time. When using single wavelengths the thickness of the films we can measure is limited by the amount of light reflected.

Other Relevant Material Information

For material information on silicon nitride ceramic visit this page

Technical Data

• Charts or specific LNF related data for this material.

References

• Citations/references for this material, review articles. If possible, examples of users publications which includes the material.