Specific Process Knowledge/Thin film deposition/Deposition of Nickel/Electroplating of nickel

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Electroplating of nickel: Danchip standard processes

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DTU Danchip Standard Programs

Four different Danchip standard programs have been made. They have all been made to fabricate nickel shims for use in the polymer injection molder at Danchip. For this purpose a nickel thickness of around 320-330 µm is required. By experimentation it has been found that the required charge for this sample thickness is 18,0 Ah. The only difference between the four different standard programs are the time required for depositing the nickel. The four different standard programs deposit 320-330 µm of nickel in about 3, 4, 6 and 12 hours respectively.

The following figure shows the current profile during the first 2 hours of the programs:

Current profiles of standard programs
Current profiles of standard programs

As can be seen from the illustration the first 30 minutes of all standard processes are identical. All processes use a slow ramping of the current. This is to make sure that some material is deposited which can conduct a higher current. Starting a plating process at several amperes is very likely to damage the sample (and possibly the sample holder) because the seed layer (usually 75-120 nm thick) cannot support that high currents.

The Standard programs are named using the following convention: DCHimmXX-YY where DCH indicates it's a process developed by Danchip, imm that is a process developed for producing samples for the injection molding machine, XX denotes the charge in Ah (Ampere-hours) and YY denotes the approximate process time in hours.

Comparison of standard processes

DCHimm18-03 DCHimm18-04 DCHimm18-06 DCHimm18-12
Expected nickel thickness 320-330 µm 320-330 µm 320-330 µm 320-330 µm
Maximum current [A]

7,5

5,5

3,5

1,5

Process time [hh:mm:ss]

02:41:01

xx:xx:xx

xx:xx:xx

12:16:01

Substrate size
  • # small samples
  • # 50 mm wafers
  • # 100 mm wafers
  • # 150 mm wafers
  • # small samples
  • # 50 mm wafers
  • # 100 mm wafers
  • # 150 mm wafers
Allowed materials
  • Allowed material 1
  • Allowed material 2
  • Allowed material 1
  • Allowed material 2
  • Allowed material 3


Example

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Deposition of silicon nitride

Deposition of silicon nitride can be done with either LPCVD (Low Pressure Chemical Vapor Deposition) or PECVD (Plasma Enhanced Chemical Vapor Deposition). Stiochiometric nitride or silicon rich (low stress) LPCVD nitride is deposited on a batch of wafers in a LPCVD nitride furnace, and PECVD nitride (or oxynitride) is deposited on a few samples at a time in a PECVD system. LPCVD nitride has a good step coverage and a very good uniformity. Using PECVD it is possible to deposit a thicker layer of nitride on different types of samples, but the nitride does not cover sidewalls very well.


Comparison of LPCVD and PECVD for silicon nitride deposition

LPCVD PECVD
Generel description Low Pressure Chemical Vapour Deposition (LPCVD furnace process) Plasma Enhanced Chemical Vapour Deposition (PECVD process)
Stoichiometry
  • Si3N4
  • SRN (only 4" nitride furnace)

Si3N4: Stoichiometric nitride

SRN: Silicon rich (low stress) nitride

  • SixNyHz
  • SixOyNzHv

Silicon nitride can be doped with boron, phosphorus or germanium

Film thickness
  • Si3N4: ~50 Å - ~1400 Å
  • SRN: ~50 Å - ~2800 Å

Thicker nitride layers can be deposited over more runs

  • ~40 nm - 10 µm
Process temperature
  • 780 oC - 845 oC
  • 300 oC
Step coverage
  • Good
  • Less good
Film quality
  • Deposition on both sides og the substrate
  • Dense film
  • Few defects
  • Deposition on one side of the substrate
  • Less dense film
  • Incorporation of hydrogen in the film
KOH etch rate (80 oC)
  • Expected <1 Å/min
  • Dependent on recipe: ~1-10 Å/min
BHF etch rate
  • Very low
  • Very high compared the LPCVD nitride
Batch size
  • 1-25 100 mm wafers
  • 1-25 150 mm wafers (only 6" furnace)

Depending on what furnace you use

  • Several smaller samples
  • 1-several 50 mm wafers
  • 1-3 100 mm wafers
  • 1 150 mm wafer

Depending on what PECVD you use

Allowed materials
  • Silicon
  • Silicon oxide
  • Silicon nitride
  • Pure quartz (fused silica)

Processed wafers have to be RCA cleaned

  • Silicon
  • Silicon oxide (with boron, phosphorous and germanium)
  • Silicon nitrides (with boron, phosphorous and germanium)
  • Pure quartz (fused silica)