Specific Process Knowledge/Thin film deposition/Deposition of Silicon Nitride

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Deposition of silicon nitride

Deposition of silicon nitride can be done by either LPCVD (Low Pressure Chemical Vapor Deposition) or PECVD (Plasma Enhanced Chemical Vapor Deposition). Stoichiometric nitride or silicon rich (low stress) LPCVD nitride is deposited on a batch of wafers in a LPCVD nitride furnace. PECVD nitride (or oxynitride) is deposited on a few samples at a time in a PECVD system. LPCVD nitride has a good step coverage and a very good uniformity. Using PECVD it is possible to deposit a much lower temperature and a thicker layer of nitride on different types of samples, but the nitride does not cover sidewalls very well.

It is also possible to deposit silicon nitride and oxynitride by reactive sputtering.

• Deposition of stoichiometric nitride using the 4" LPCVD nitride furnace
• Deposition of silicon rich (low stress) nitride using the 6" LPCVD nitride furnace

• Nitride deposition using PECVD (or oxynitride)

• Nitride deposition using Lesker sputter system

Comparison of LPCVD, PECVD and Lesker sputter system for silicon nitride deposition

	LPCVD	PECVD	Lesker sputter system
Generel description	Low Pressure Chemical Vapour Deposition (LPCVD furnace process)	Plasma Enhanced Chemical Vapour Deposition (PECVD process)	Reactive sputtering
Stoichiometry	Stoichiometric nitride, Si3N4 Silicon rich (low stress) nitride, SRN	SixNyHz SixOyNzHv Silicon nitride can be doped with boron or phosphorus	Unknown
Film thickness	Stoichiometric nitride: ~5 nm - ~230 nm Silicon rich (low stress) nitride: ~5 nm - ~335 nm Thicker nitride layers can be deposited over more runs (maximum two)	~40 nm - 10 µm	limited by process time. Deposition rate is ~1.7nm/min
Process temperature	Stoichiometric nitride: 780 oC - 800 oC Silicon rich (low stress) nitride: 810 oC - 845 oC	300 oC	Room temperature (higher temperature possible)
Step coverage	Good	Less good	yes, but amount unknown
Film quality	Deposition on both sides og the substrate Dense film Few defects	Deposition on one side of the substrate Less dense film Incorporation of hydrogen in the film	Deposition on one side of the substrate unknown quality
KOH etch rate (80 oC)	Expected <1 Å/min	Dependent on recipe: ~1-10 Å/min	Unknown
BHF etch rate	Very low	Very high compared the LPCVD nitride	Unknown
Batch size	1-15 100 mm wafers (4" furnace), 1-25 100 mm wafers (6" furnace) 1-25 150 mm wafers (only 6" furnace)	Several smaller samples 1-7 50 mm wafers 1 100 mm wafers 1 150 mm wafer Depending on what PECVD you use	Several smaller samples 1-several 50 mm wafers 1*100 mm wafers 1*150 mm wafer
Allowed materials	Silicon Silicon oxide Silicon nitride Pure quartz (fused silica) Processed wafers have to be RCA cleaned	Silicon Silicon oxide (with boron, phosphorous) Silicon nitrides (with boron, phosphorous) Pure quartz (fused silica) III-V materials (in PECVD4) Small amount of metals (in PECVD3)	Any