Specific Process Knowledge/Thin film deposition/Deposition of polysilicon/Deposition of polysilicon using LPCVD/Standard recipes, QC limits and results for the 6" polysilicon furnace

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Standard recipes on the 6" polysilicon furnace (this recipe is being watched in the in the quality assurance program):

Quality Controle (QC) for the 6" LPCVD polysilicon furnace

The QC procedure for the 6" LPCVD polysilicon furnace The newest QC data for the 6" LPCVD polysilicon furnace QC recipe "POLY" Standard polysilicon Wafer size and number of wafers 4" wafers 25 wafers in a run 6" wafers 25 wafers in a run Deposition time 30 min SiH4 (silane) flow 70 sccm Pressure 200 mTorr Temperature (zone 1, 2, 3, 4, 5) 625oC, 620oC, 616oC, 623oC, 624oC QC limits (+/- 3 times the standard deviation) 4" wafers 6" wafers Polysilicon deposition rate and non-uniformity over the center wafer 5.96 - 10.01 nm/min < 3.0 % 5.51 - 8.91 nm/min < 3.0 % Polysilicon deposition rate and non-uniformity over the boat 5.85 - 9.88 nm/min < 5.0 % 5.62 - 8.75 nm/min < 5.0 %

Expected results when using the standard recipes on the 6" polysilicon furnace:

	QC Recipe	Polysilicon deposition rate [nm/min]	Standard deviation for the polysilicon deposition rate [%]	Refractive index	Standard deviation for the refractive index [%]
Over the center wafer 4" wafers Average values, Jul. 2012 - Nov. 2022	"POLY"	7.99	0.68	3.95	0.04
Over the boat 4" wafers Average values, Jul. 2012 - Nov. 2022	"POLY"	7.87	0.67	3.95	0.05
Over the center wafer 6" wafers Average values, Mar. 2013 - Sep. 2021	"POLY"	7.21	0.57	3.96	0.02
Over the boat 6" wafers Average values, Mar. 2013 - Sep. 2021	"POLY"	7.19	0.52	3.96	0.03

Process parameters for the standard recipes on the 6" LPCVD polySi furnaces:

Recipe name	Wafer size and number of wafers	polySi thickness [nm]	Temperature [oC]	Pressure [mTorr]	SiH4 gas flow [sccm]	BCl3 gas flow [sccm]	Comments
"POLY"	4" or 6" wafers 1-25 wafers	0 - 2000	616-625	200	70	0
"DOPDPOLY"	4" or 6" wafers 1-25 wafers	0 - 1000	596-600	150	50	1	Boron doping not available at the moment
"AMORPH"	4" or 6" wafers 1-25 wafers	0 - 2000	562-565	200	70	0
"DOPEAMOR"	4" or 6" wafers 1-25 wafers	0 - 2000	556-565	150	50	1	Boron doping not available at the moment

Expected results when using the standard recipe on the 6" LPCVD polySi furnace:

These are typical values

Recipe name	Deposition rate [nm/min]	Refractive index@630nm	Thickness variation on center wafer	Thickness variation along the boat	Surface roughness [nm]	Sheet resistance [Ohms/square]	Boron concentation [boron atoms/cm3]	Comments
"POLY"	~ 8-9 (4" wafers)	~ 3.9	< 2%	< 4%	~ 5.66, measured with AFM standard tip (244 nm layer) AFM image for surface roughness measurement. 244 nm polySi deposited using the "POLY" recipe.			See quality control data for latest measurements. Standard polySi not part of the acceptance test.
"DOPEPOLY"	~ 4.0-4.1 (4" wafers)		< 2% Acceptance test March 2012: 1.29%-1.38% (4" wafers)	< 4% Acceptance test March 2012: 1.63%-1.81% (4" wafers)	~ 4.83, measured with AFM standard tip (273 nm layer) AFM image for surface roughness measurement. 273 nm boron doped polySi deposited using the "DOPDPOLY" recipe.	~155-175 Acceptance test March 2012: 157-171, variation over boat 4.5% (4" wafers)	~ 1021 boron atoms/cm3. "Dopepoly" recipe, 30 minutes deposition, Poly-Si thickness is ~104nm, Aug. 2014. Boron concentration measured by SIMS through a boron doped poly-Si layer on 110nm Silicon dioxide, N-type Si(100) Substrate.	Run-to-run uniformity, acceptance test March 2012: 1.43 % (4" wafers, 3 runs)
"AMORH"	~ 2.2-2.3 (4" wafers)	~ 4.54 (see below)	< 2% Acceptance test August 2011: 0.80%-1.39% (6" wafers)	< 4% Acceptance test August 2011: 0,45%-0.78% (6" wafers)	~ 0.47, measured with AFM standard tip (134 nm layer) AFM image for surface roughness measurement. 244 nm amorphous polySi deposited using the "AMORPOLY" recipe.			Run-to-run uniformity, acceptance test August 2011: 0.29 % (6" wafers, 3 runs)

The deposition rate changes a little over time, but generally it is fairly good from run to run. The last measured values of the polySi thicknesses can be found on the Poly Si page in the 6" Furnace logbook and in the quality control data (only standard polySi).

Amorphous Si measurement

For amorphous LPCVD Si deposited in August 2022 an ellipsometer measurement and a SEM measurement have been made. The amorphous Si was deposited on a 4" wafer with thermal wet SiO₂.

For the SEM measurement the wafer was first cleaved, and then the layer thicknesses were measured. As seen from the SEM pictures below, the thickness of the amorphous Si layer was measured to be 895 nm, and the thickness of the SiO₂ layer was measured to be 314 nm.

SEM measurement of amorphous LPCVD silicon deposition on a Si wafer with SiO₂

For the ellipsometer measurement, it was tried to measure the thickness and the optical parameters using different models. Below the best measurement result is show and also the refractive index (n) and the extinction coefficient (k) as function of wavelength. The thickness of the amorphous Si layer is measured to be 929.75 nm, and at 632.8 nm wavelenght n is 4.54 and k is 1.18. The thickness of the SiO₂ layer is measured to be 314.14 nm.

Results of the ellipsometer measurement

Refractive index (n) and extinction coefficient (k) as function of wavelength

By comparing the SEM and the ellipsometer measurements, it can be seen that not exactly the same thickness of the amorphous Si layer is measured. This indicates the the optical parameters measured by the ellipsometer might also be a bit off, even though the measurement fits very well to the model.