Specific Process Knowledge/Thin film deposition/Deposition of Silicon Nitride/Deposition of Silicon Nitride using PECVD/PECVD3: Low stress nitride testing

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Stress variation with LF/HF timing (Thomas Pedersen @ DTU Nanolab 2018)

In late 2018 a series of experiments trying to control the stress level in silicon nitride deposited on PECVD3 were made. The only parameter changed was the timing between the high frequency and low frequency periods. Experiments were made on 690 µm thick 6" wafers, no quartz carrier was used. Default parameters of the mfsinls2 recipe are listed below.

SiH4 [sccm]	NH3 [sccm]	N2 [sccm]	Pressure [mTorr]	HF Time [s]	HF Power [W]	HF Load [%]	HF Tune [%]	LF Time [s]	LF Power [W]	LF Load [%]	LF Tune [%]
30	30	1470	845	7.8	100	70	68	2.2	100	5.4	48.8

Timing changes and measured stress are listed below.

Date	Time [mm:ss]	HF Time [s]	LF Time [s]	Thickness [nm]	Std.Dev [nm]	Rate [nm/min]	RI []	Stress [Mpa]
20-08-2018	23:00	7.8	2.2	1143	23	48.1	2.040	127	Tensile
24-08-2018	23:00	7.3	2.7	1184	15	51.5	2.040	96	Tensile
04-09-2018	22:00	6.0	4.0	1190	13	54.1	2.000	41.5	Compressive
04-09-2018	18:30	5.8	4.2	1007	9	54.4	2.010	42.2	Compressive
11-09-2018	18:30	5.5	4.5	1026	9	55.5	2.001	90	Compressive
22-10-2018	18:30	11.2	8.8	1008	6.2	54.5	2.011	61	Compressive

The stress as function of percent LF power is plotted in the graph below.

DOE made to find a good QC nitride recipe with low stress and low KOH etch rate (by Berit Herstrøm @ DTU Nanolab 2016 Marts)

Analysis of KOH etch rate dependency of process parameters
Analysis of film stress dependency of process parameters