Specific Process Knowledge/Thin film deposition/Furnace LPCVD PolySilicon

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LPCVD (Low Pressure Chemical Vapor Deposition) PolySilicon

A4 Furnace PolySilicon (situated in cleanroom 2

Danchip has two furnaces for deposition of LPCVD polysilicon: A new 6" furnace (installed in 2011) for deposition of standard polySi, amorphous polySi and boron doped polySi on 4" or 6" wafers and an older 4" furnace (installed in 1995) for deposition of standard polySi, amorphous polySi, boron- and phosphorous doped polySi on 4" wafers. In LabManager the two furnaces are named "Furnace: LPCVD Poly-Si" and "Furnace: LPCVD Poly-Silicon 6inch", respectively. Both furnaces are Tempress horizontal furnaces.

The LPCVD polysilicon deposition is a batch process, where polySi is deposited on a batch of 25 or 50 wafers (6" polySi furnace) or 30 wafers (4" polySi furnace). The polySi has a good step coverage, and especially for standard polySi the film thickness is very uniform over the wafers.

The reactive gas is silane (SiH4). The dopant for boron doped polySi is BCl3 (6" polySi furnace) or B2H6 (4" polySi furnace), and for phosphorous doped polySi the dopant is PH3. For standard polysilion the deposition takes place at a temperature of 620oC and a pressure of 200-250 MTorr. For amorphous polysilicon the deposition temperatures and thus the deposition rate are lower, and for boron and phosphorous doped polySi the deposition temperature is 600oC - 620oC depending on whether you use the 6" or the 4" polySi furnace. For phousphorous doped polySi the deposition rate is approximately ten times lower than for boron doped polySi. More process information about the process parameters can be found in the table below.

To get information on how to operate the furnaces please read the user manuals which are uploaded to the machine pages in LabManager or consult the Furnace group at Danchip (furnace@danchip.dtu.dk).

Process Knowledge

Please take a look at the process side for deposition of Silicon Nitride using LPCVD: Deposition of Silicon Nitride using LPCVD


Overview of the performance of the LPCVD polysilicon processes and some process related parameters

Purpose Deposition of LPCVD polysilicon

6" furnace:

  • Standard polySi
  • Amorphous polySi
  • Boron doped polySi (BCl dopant)

4" furnace:

  • Standard polySi
  • Amorphous polySi
  • Boron doped polySi (BH dopant)
  • Phosphorus doped polySi
Performance Film thickness

6" furnace:

  • Standard polySi: 0-2000 nm
  • Amorphous polySi: 0-1000 nm
  • Boron doped polySi: 0-1000 nm

4" furnace

  • Standard polySi: 0-2000 nm
  • Amorphous polySi: 0-2000 nm
  • Boron doped polySi: 0-2000 nm
  • Phosphorus doped polySi: 0-1000 nm
Step coverage
  • Good
Thickness uniformity
  • Good
Process parameter range Process Temperature

6" furnace:

  • Standard polySi: 620 oC
  • Amorphous polySi: 560-580 oC
  • Boron doped polySi: 600-620 oC

Note: The process temperature depends vary over the furnace tube 4" furnace:

  • Standard polySi: 620 oC
  • Amorphous polySi: 560-580 oC
  • Boron doped polySi: 620 oC
  • Phosphorus doped polySi: 620 oC

The process temperature depends vary over the furnace tube

Process pressure
  • 150-250 mTorr

The process pressure depends on the actual process

Gas flows

6" furnace:

  • SiH: 50-70 sccm
  • BCl: 1 sccm

The silane (SiH) flow depends on the actual process 4" furnace:

  • SiH: 80 sccm
  • BH: 7 sccm
  • PH: 7 sccm
Substrates Batch size

6" furnace:

  • 1-25 4" wafers or 6" wafers per run
  • 1-30 4" wafers per run

Deposition on both sides of the substrate

Substrate materials allowed
  • Silicon wafers (new from a clean box or RCA cleaned)
    • with layers of silicon oxide or silicon (oxy)nitride
  • Quartz wafers (RCA cleaned)