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 the deposition of PolySilicon using Low Chemical Vapour Deposition (LPCVD).

We have a 6" furnace (installed in 2011) for the 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 the 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 with the Lesker Sputter systems (both the single chamber and dual chamber systems). One of the advantages of sputtering is that you can deposit on almost any material you like. In the cluster system you can heat the substrate up to 600 °C.

• 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.

Some parameters for sputter deposition of Si in the now-decomissioned Wordentec are found 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), where the substrate can be heated up to 250 °C. 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.

• Si evaporation in E-beam evaporator (10-pockets)

Comparison of the methods for deposition of Silicon

	4" and 6" Furnace PolySi (Furnace LPCVD PolySi)	PECVD (PECVD)	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.	E-beam evaporation of Si.
Doping facility	Yes, B (boron) and P (phosphorus)	Yes, B and P	None	None	None
Pre-clean	New wafers can go directly into the furnace. Processed wafers have to be RCA cleaned		None	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 >200 nm	few nm to ?	few nm to 600 nm
Deposition rate	undoped, boron doped:~100 Å/min Phosphorous doped:~20 Å/min	~6 Å/s can probably be higher	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 to 600 °C	room temperature to 250 °C
Step coverage	Good	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	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, see cross-contamination sheet	Almost any that does not degas at your intended substrate temperature. See also cross-contamination sheets.	Almost any that does not degas at your intended substrate temperature. See also cross-contamination sheet.
Allowed material	*Only those above (under allowed substrates).	See the cross contamination sheets	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