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					Plasma-enhanced
     CVD.
       Lev Berkovich
          MSE 550
    Professor B. Bavarian
       March 21, 2005
   Plasma-enhanced CVD

 Relation of PECVD to other processes
 Typical processes and hardware
 Specific applications
 Examples of PECVD modeling
  software
PECVD and other CVD processes.
     What is Plasma-enhanced CVD
   Plasma Enhanced CVD (PECVD) is a process where glow-discharge plasma is
    sustained in a reaction chamber. This technology was developed to meet a
    demand from the semiconductor industry to have a low temperature process of
    silicon nitride films for the passivation and insulation of the complete devices,
    that could not be exposed to the temperatures that are normal for the CVD
    ~1000 0C.
   The most common way to excite the plasma is the RF field. PECVD is mostly
    used to deposit dielectrics, and therefore the DC excitation will not work.
    Frequency range is usually from 100kHz to 40MHz. The process does not
    require a deep vacuum, so the reduced pressure between 50 mtorr to 5 torr is
    used. The ion density is usually between 109 – 1011 1/cm3 and average electron
    energies are between 1 to 10 eV.
   Presence of plasma changes the thermodynamics of surface reactions and
    considerably lowers the temperature at which reactions are possible. For
    instance, for TiC the deposition reaction is not thermodynamically possible
    bellow 1218 0K. However, in a presence of plasma, the reaction is possible at as
    low as 700 0K.
   The following table provides a sampling of materials deposited by the PECVD
    process.
PECVD films, Source gases and
  Deposition Temperatures
                   PECVD reactors
   Tube or tunnel reactor
                   PECVD reactors
   Reinberg-type cylindrical reactor
              PECVD reactors
•ECR plasma deposition reactors
               Applications of PECVD
   ULSI-DRAM memory cells
              Applications of PECVD.
Chemical Vapor   Deposition (CVD) of Teflon™-like Films
               Applications of PECVD
   Low Energy Plasma Enhanced CVD (LEPECVD)
               Applications of PECVD
   Nano-Master PECVD systems
             Applications of PECVD
•Plasma Induced Surface Modifications
•Plasma Cleaning
•Plasma Reactive Ion Etching
•Plasma Polymerization
•Plasma Enhanced Chemical Vapor Deposition (PECVD) of
•SiO2, Si3N4, DLC, and other films
                                      Applications of PECVD
low stress silicon oxide                                 compressive stress silicon nitride (Si:N)
thickness range:                1000 to 10000 nm         thickness range:                 100 to 1500 nm
thickness non-uniformity:       < ±2.5% (across wafer)   thickness non-uniformity:        < ±2.5% (across wafer)
deposition temperature:         300°C                    deposition temperature:          300°C
refractive index (633 nm):      1.50±0.02                refractive index (633 nm):       2.04±0.015
mechanical stress:              230 MPa (tensile)        mechanical stress:               520±20 MPa (compressive)
dielectric constant:            4.1                      dielectric constant:             4.1
                                                         tensile stress silicon nitride (Si:N)
tensile stress silicon oxide                             thickness range:                 100 to 10000 nm
thickness range:                100 to 2000 nm           thickness non-uniformity:        < ±4.0% (across wafer)
thickness non-uniformity:       < ±3.0% (across wafer)   deposition temperature:          300°C
deposition temperature:         300°C                    refractive index (633 nm):       2.03±0.02
refractive index (633 nm):      1.50±0.02                mechanical stress:               440±150 MPa (tensile)
mechanical stress:              230 MPa (tensile)        dielectric constant:             4.1
dielectric constant:            4.1                      silicon oxi-nitride (Si:N:O)
low stress silicon nitride (Si:N)                        thickness range:                 100 to 10000 nm
thickness range:                100 to 3000 nm           thickness non-uniformity:        < ±3.0% (across wafer)
thickness non-uniformity:       < ±3.0% (across wafer)   deposition temperature:          300°C
deposition temperature:         300°C                    refractive index (633 nm):       1.569±0.003
refractive index (633 nm):      2.00±0.01                mechanical stress:               <±30 MPa (tensile)
mechanical stress:              <±50 MPa (tensile)       dielectric constant:             4.1
dielectric constant:            4.1
PECVD modeling and computerized
           control
PECVD modeling and computerized
           control
                    Conclusion

An impressive number of different CVD materials -
metals, semiconductors, oxides, nitrides, carbides,
diamonds, etc. ) present technical interest for a variety
of applications. The PECVD is particularly interesting
due to the relatively low process temperatures,
allowing for the processing of the complete micro-
electronic devices.