Specific Process Knowledge/Thin film deposition/Furnace LPCVD PolySilicon

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Deposition of silicon using LPCVD

4" polysilicon furnace (B4) located in cleanroom B-1

6" polysilicon furnace located (E2) in cleanroom E-6

DTU Nanolab has two furnaces for deposition of LPCVD (Low Chemical Vapour Deposition) silicon: A 6" furnace (installed in 2011) for deposition of standard polySi, amorphous Si and boron doped polySi on 100 mm or 150 mm wafers and a 4" furnace (installed in 1995) for deposition of standard polySi, amorphous Si, boron- and phosphorous doped polySi on 100 mm wafers. In LabManager the two furnaces are named "Furnace: LPCVD Poly-Si (4") (B4)" and "Furnace: LPCVD Poly-Si (6") (E2)", respectively. Both furnaces are Tempress horizontal furnaces.

The LPCVD silicon deposition is a batch process, where silicon is deposited on a batch of 25 or 50 wafers (6" polySi furnace) or 30 wafers (4" polySi furnace). The silicon 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 - only available at request (6" polySi furnace) or B₂H₆ (4" polySi furnace), and for phosphorous doped polySi the dopant is PH₃ (4" polySi furnace). For standard and doped polysilion the deposition takes place at a temperature of 600 ^oC - 620 ^oC and a pressure of 200-250 mTorr. For amorphous silicon the deposition temperature is lower, and thus the deposition rate is also lower. For phosphorus doped polySi the deposition rate is approximately ten times lower than for standard and boron doped polySi. Please check the cross contamination information in LabManager before you use any of the two furnaces.

The user manuals, quality control procedures and results, technical information and contact information can be found in LabManager:

4" LPCVD polysilicon furnace (B4)

6" LPCVD polysilicon furnace (E2)

Furnace computer manual

Manual for the furnace computer to the A, B, C and E stack furnaces

The A, B, C and E stack furnaces can be controlled either from a touch screen by each furnace or from a furnace computer. The user manual for the furnace computer can be found here:

Manual for furnace computers for the A, B, C and E stack furnaces

Process information

• Deposition of polysilicon using the 4" polysilicon furnace
• Boron doped poly-Si and a-Si by using 4" polysilicon furnace

• Deposition of polysilicon using the 6" polysilicon furnace
• Boron doped poly-Si using 6" polysilicon furnace

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

Equipment		4" LPCVD polysilicon furnace (B4)	6" LPCVD polysilicon furnace (E2)
Purpose	Deposition of	Standard polySi Amorphous polySi Boron doped polySi (B2H6 dopant) Phosphorus doped polySi (PH3 dopant)	Standard polySi Amorphous polySi Boron doped polySi (BCl3 dopant)
Performance	Step coverage	Very Good	Very good
	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 a-Si: 580 oC Phosphorus doped a-Si: 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	200-250 mTorr	150-220 mTorr The process pressure depends on the process
	Gas flows	SiH4: 80 sccm B2H6: 7 sccm PH3: 7 sccm	SiH4: 50-70 sccm BCl3: 1 sccm The silane (SiH4) flow depends on the process
Substrates	Batch size	1-30 100 mm wafers Including a testwafer with ~110 nm oxide	1-25 or 1-50 100 mm wafers 1-25 or 1-50 150 mm wafers Including a testwafer with ~110 nm oxide
	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)

Rules for storage and RCA cleaning of wafers to the B4 and E2 furnaces

• Storage and cleaning of wafer to the B4 and E2 furnaces