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 polysilicon using the 4" polysilicon furnace
• Deposition of polysilicon using the 6" polysilicon furnace

Deposition of Silicon using PECVD

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

• Si deposition using PECVD3

Deposition of Silicon using sputter deposition

At Nanolab we can sputter silicon the using Wordentec or the Lesker Sputter systems. One of the advantages of sputtering is that you can deposit on almost any material you like.

• Si sputter deposition in the Wordentec
• Si sputter deposition in the Sputter-System (Lesker) - includes information on surface roughness and stress
• Si sputter deposition in the Sputter-System Metal-Oxide(PC1)
• Si sputter deposition in the Sputter-System Metal-Oxide(PC3)

It was previosly possible to sputter Si with our IonFab 300. You can read about the deposition conditions and results from that here.

Deposition of Silicon using e-beam evaporation

It is possible to e-beam evaporate silicon at Nanolab using the E-beam evaporator (10-pockets). As with sputtering you can deposit on almost any material. In e-beam evaporation the deposition is line-of-sight and will be suitable for lift-off. However for 8" wafers the system is not optimized for lift-off on the full diameter of the wafer.

Comparison of the methods for deposition of Silicon

	4" and 6" Furnace PolySi (Furnace LPCVD PolySi)	PECVD (PECVD)	Sputter (Wordentec)	Sputter (Lesker)	Sputter (Sputter-system Metal-Oxide (PC1) and Sputter-system Metal-Nitride (PC3))	E-beam evaporation (E-beam evaporator (10-pockets))
General description	LPCVD (low pressure chemical vapour deposition) of a-Si and poly-Si	Plasma Enhanced Chemical Vapor Deposition of Si	Sputter deposition of Si.	Sputter deposition of Si.	Sputter deposition of Si.	E-beam evaporation of Si.
Doping facility	Yes, B (boron) and P (phosphorus)	Yes, B and P	None	None	None	None
Pre-clean	New wafers can go directly into the furnace. Processed wafers have to be RCA cleaned		RF Ar clean available	RF Ar clean available	RF Ar clean available	None
Layer thickness	~5 nm to 2 µm, if thicker layers are needed please ask the furnace team.	few nm to ~ 600 nm	few nm to ~ 300 nm	few nm to >200 nm	few nm to ?	few nm to 100 nm *
Deposition rate	undoped, boron doped:~100 Å/min Phosphorous doped:~20 Å/min	~6 Å/s can probably be higher	On the order of 1 Å/s dependent on process parameters. See more here.	Depends on process parameters, roughly 0.2-2 Å/s. See Process Log.	Depends on process parameters, at least 0.3 Å/s, see conditions here	1 Å/s
Process temperature	560 °C (amorphous) and 620 °C (poly)	300 °C	room temperature	room temperature	room temperature to 600 °C	room temperature to 250 °C
Step coverage	Good	Medium	Medium	Medium	Medium - may be possible to improve using HIPIMS	no step coverage unless using tilt holder, in which case the step coverage can be very good and can be tuned.
Adhesion	Good for fused silica, silicon oxide, silicon nitride, silicon	Not tested, but do not deposit on top of silicon
Batch size	1-30 wafers (4" furnace) 1-25 wafes (6" furnace)	Several small samples 1-2x 50 mm wafer 1x 100 mm wafer 1x 150 mm wafer	24x 2" wafers or 6x 4" wafers or 6x 6" wafers	Up to 1x6" wafers smaller pieces	Up to 10x6" or 4" wafers many smaller pieces	Up to 4 x 6" wafer or 3x 8" wafers (ask for special holder) Many smaller pieces
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)	See the cross contamination sheets	Almost any that does not degas.	Almost any that does not degas, see cross-contamination sheet	Almost any that does not degas, see cross-contamination sheets	Almost any that does not degas, see cross-contamination sheets
Allowed material	*Only those above (under allowed substrates).	See the cross contamination sheets	Almost any that does not degas.	Almost any that does not degas, see the cross-contamination sheet	Almost any that does not degas, see the cross-contamination sheets	Almost any that does not degas, see cross-contamination sheet
Comment		Only in PECVD3				Please only deposit Si on the afternoon before a scheduled service as it can result in many flakes in the chamber. See the booking calendar or ask staff to find out when the next service will be.

* If you wish to deposit a thicker layer than 100 nm please talk to responsible staff or write to thinfilm@nanolab.dtu.dk