Specific Process Knowledge/Thin film deposition/Furnace LPCVD PolySilicon

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LPCVD (Low Pressure Chemical Vapor Deposition) PolySilicon

6" polysilicon furnace located (E2) in cleanroom 14

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 620 ^oC 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 600 ^oC - 620 ^oC 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.

The user manual(s), quality control procedure(s) and results, technical information and contact information can be found in LabManager:

4" LPCVD polysilicon furnace (B4)

6" LPCVD polysilicon furnace (E2)

Process information

Deposition of polysilicon using LPCVD

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

Equipment		4" LPCVD polysilicon furnace (B3)	6" LPCVD polysilicon furnace (E2)
Purpose	Deposition of	Standard polySi Amorphous polySi Boron doped polySi (B₂H₆ dopant) Phosphorus doped polySi	4" furnace: Standard polySi Amorphous polySi Boron doped polySi (BCl₃ dopant)
Performance	Step coverage	Very Good	Very good
Performance	Film quality	Deposition on both sides of the substrate Good uniformity over the wafer	Deposition on both sides of the substrate Good uniformity over the wafer
Process parameter range	Process Temperature	Standard polySi: 620 ^oC Amorphous polySi: 560-580 ^oC Boron doped polySi: 620 ^oC Phosphorus doped polySi: 620 ^oC	Standard polySi: 620 ^oC Amorphous polySi: 560-580 ^oC Boron doped polySi: 600-620 ^oC The process temperature vary over the furnace tube
	Process pressure	250 mTorr	150-220 mTorr The process pressure depends on the actual process
	Gas flows	SiH₄: 80 sccm B₂H₆: 7 sccm PH₃: 7 sccm The silane (SiH₄) flow depends on the actual process	SiH₄: 50-70 sccm BCl₁: 1 sccm
Substrates	Batch size	1-20 100 wafers Including a testwafer with ~110 nm oxide	1-25 (or 50) 100 mm wafers 1-25 (or 50) 150 mm wafers Including a testwafer with ~110 nm oxide
Substrates	Substrate materials allowed	Silicon wafers (new or RCA cleaned) with layers of silicon oxide or silicon (oxy)nitride from the A, B and E stack furnaces Quartz/fused silica wafers (RCA cleaned)	Silicon wafers (new or RCA cleaned) with layers of silicon oxide or silicon (oxy)nitride from the A, B and E stack furnaces Quartz/fused silica wafers (RCA cleaned)