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 with either LPCVD (Low Pressure Chemical Vapor Deposition) or PECVD (Plasma Enhanced Chemical Vapor Deposition). Stochiometric nitride or silicon rich (low stress) LPCVD nitride is deposited on a batch of wafers in a LPCVD nitride furnace, and 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 using the Lesker sputter system. However, the process hasnot been tested yet, but the required sputter targets for nitride deposition are avaliable.

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	Si_xN_yH_z Si_xO_yN_zH_v Silicon nitride can be doped with boron, phosphorus or germanium	Unknown
Film thickness	Stoichimetric 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	1-25 100 mm wafers 1-25 150 mm wafers (only 6" furnace)	Several smaller samples 1-several 50 mm wafers 1-3 100 mm wafers 1 150 mm wafer Depending on what PECVD you use	Several smaller samples 1-several 50 mm wafers 1100 mm wafers 1150 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 and germanium) Silicon nitrides (with boron, phosphorous and germanium) Pure quartz (fused silica)	Any