Specific Process Knowledge/Thin film deposition/Deposition of Silicon

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PolySilicon can be deposited in several Nanolab tools. It can be sputtered, e-beam evaporated or be deposited in the PolySilicon furnaces. In the chart below you can compare the different deposition methods:

Deposition of PolySilicon using LPCVD

DTU Nanolab has two furnaces for deposition of LPCVD (Low Chemical Vapour Deposition) polysilicon: A 6" furnace (installed in 2011) for deposition of standard polySi, amorphous polySi and boron doped polySi on 100 mm or 150 mm wafers and a 4" furnace (installed in 1995) for deposition of standard polySi, amorphous polySi, 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.

Deposition of Silicon using sputter deposition technique

At Nanolab you can also deposit silicon the using Wordentec, the Lesker Sputter systems or the IBE Ionfab300 sputter systems. One of the advantages here is that you can deposit on any material you like.

Deposition of Silicon using PECVD

At Nanolab you can also deposit silicon the using PECVD. The deposition temperature is 300 ^oC.

Si deposition using PECVD3

Comparison of the methods for deposition of Silicon

	4" and 6" Furnace PolySi (Furnace LPCVD PolySi)	Sputter (Wordentec)	Sputter (IBE/IBSD Ionfab 300)	Sputter (Lesker)	PECVD (PECVD)
General description	LPCVD (low pressure chemical vapour deposition) of polysilicon	Sputter deposition of Si.	Ion beam sputter deposition of Si.	Sputter deposition of Si.	Plasma Enhanced Chemical Vapor Deposition.
Doping facility	Can be doped with boron or phosphorus during deposition	None	None	None	Yes, B and P
Pre-clean	New wafers can go directly into the furnace. Processed wafers have to be RCA cleaned	RF Ar clean	None	RF Ar clean
Layer thickness	~50Å to 2µm, if thicker layers are needed please ask the furnace team.	10Å to about 3000Å	No defined limits		few nm to ~500nm
Deposition rate	undoped, boron doped:~100Å/min Phosphorous doped:~20Å/min	In the order of 1 Å/s, but dependent on process parameters. See more here.	About 5 nm/min. See more here.	Depends on process parameters, roughly 1 Å/s.	~6Å/s can probably be higher
Process temperature	560 ^oC (amorph) and 620 ^oC (poly)	?	Platen: 5-60 ^oC	Wafers can be heated to 100-200°C	300 ^oC
Step coverage	Good	.	Not known		Medium
Adhesion	Good for fused silica, silicon oxide, silicon nitride, silicon	.	Not tested		Not tested, but do not deposit on top of silicon
Batch size	1-30 wafers (4" furnace) 1-25 wafes (6" furnace)	24x 2" wafers or 6x 4" wafers or 6x 6" wafers	Several small samples mounted with capton tape 1x 50 mm wafer 1x 100 mm wafer 1x 150 mm wafer 1x 200 mm wafer	Up to 1x6" wafers smaller pieces	Several small samples 1-2x 50 mm wafer 1x 100 mm wafer 1x 150 mm wafer
Allowed substrates	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 Quartz wafers Pyrex wafers	Same materials as on the allowed materials below	Silicon wafers Quartz wafers Pyrex wafers	See the cross contamination sheet for PECVD3
Allowed material	Only those above (under allowed substrates).	Silicon oxide Silicon (oxy)nitride Photoresist PMMA Mylar SU-8 Metals	Silicon, silicon oxides, silicon nitrides Metals from the +list Metals from the -list Alloys from the above list Stainless steel Glass III-V materials Resists Polymers Capton tape	Silicon oxide Silicon (oxy)nitride Photoresist Metals	See the cross contamination sheet for PECVD3
Comment			The system is used both for IBSD and IBE. Si deposition can only be performed when it is set up for IBSD.		Only in PECVD3