Specific Process Knowledge/Thin film deposition/Furnace LPCVD Nitride

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6" LPCVD nitride furnace (E3) located in cleanroom E-6

4" LPCVD nitride furnace (B2) located in cleanroom B-1

Deposition of Silicon Nitride using LPCVD

DTU Nanolab has two LPCVD (Low Pressure Chemical Vapour Deposition) furnaces for deposition of silicon nitride:

• A 4" furnace (installed in 1995) for deposition og stoichiometric nitride on 4 inch wafers.
• A 6" furnace (installed in 2008) for deposition of low stress/silicon rich nitride on 4 inch and 6 inch wafers. Deposition of stoichiometric nitride on 4 inch wafers is also allowed in this furnace.

In LabManager the two furnaces are named "Furnace: LPCVD nitride (4") (B2)" and "Furnace: LPCVD nitride (6") (E3)", respectively. Both furnaces are Tempress horizontal furnaces.

Please check the cross contamination information in LabManager before you use any of the two furnaces.

The LPCVD silicon nitride deposition is a batch process, where nitride can be deposited on a batch of up to 15 wafers (in the 4" nitride furnace) or 25 wafers (in the 6" nitride furnace) at a time. The deposition takes place under vacuum (120-200 mTorr, depending on the process) and at high temperature (780-845 C, depending on the process). The reactive gases are ammonia (NH₃) and dichlorsilane (SiH₂Cl₂).

The LPCVD nitride has a very good step coverage, and the film thickness is very uniform over the wafers.

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

4" LPCVD nitride furnace (B2),

6" LPCVD nitride furnace (E3)

Process information

• Deposition of low stress nitride using the 4" LPCVD nitride furnace (No longer available to deposit low stress nitride by 4" LPCVD nitride furnace)
• Deposition of stoichiometric nitride using the 4" LPCVD nitride furnace
• Deposition of stoichiometric nitride using the 6" LPCVD nitride furnace (Only available for 6" wafers and special permission required)
• Deposition of low stress nitride using the 6" LPCVD nitride furnace
• Using LPCVD silicon nitride as a masking material for KOH etching

Rules for storage and RCA cleaning of wafers to the B stack furnaces

• Storage and cleaning of wafer to the B stack furnaces

Equipment performance and process related parameters

Equipment		6" LPCVD nitride furnace (E3)	4" LPCVD nitride furnace (B2)
Purpose	Deposition of	Silicon rich (low stress) nitride Stoichiometric nitride	Stoichiometric nitride
Performance	Step coverage	Very good	Very good
	Film quality	Deposition on both sides of the substrate Dense film Few defects	Deposition on both sides of the substrate Dense film Very few defects
Process parameter range	Temperature	810-845 oC The temperature vary over the furnace tube	780-790 oC The temperature vary over the furnace tube
	Pressure	150 mTorr	200 mTorr
	Gas flows	For Low stress nitride Dichlorsilane (SiH2Cl2): 200 sccm Ammonia (NH3): 50 sccm For Stoichiometric nitride on 6" wafers Dichlorsilane (SiH2Cl2): 45 sccm Ammonia (NH3): 180 sccm	Dichlorsilane (SiH2Cl2): 20 sccm Ammonia (NH3): 80 sccm The gas flows depend on whether nitride is deposited on 4" or 6" wafers
Substrates	Batch size	1-25 100 mm wafers 1-25 150 mm wafers Including a test wafer	1-15 100 mm wafers Including a test wafer
	Allowed materials	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)