Specific Process Knowledge/Thin film deposition/Furnace LPCVD PolySilicon/Phosphorous doped poly-Si

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Phosphorous doped poly silicon by using B4 4" LPCVD polysilicon furnace

Result from Niccolò Bottauscio, DTU Nanolab, November 2025

Process parameters

Recipe: POLYPH3
Deposition time: 2 hours
Temperature: 525 °C (zone 1), 518 °C (zone 2), 525 °C (zone 3)
Pressure: 200 mtorr
Silane (SiH₄)/N₂ flow: 80 sccm
Phosphine (PH₃)/N₂ flow: 7 sccm

Annealing: No annealing afterwards

Wafer positions:

Test wafers: w6 (towards furnace), w15 (center), w24 (towards door)
Dummy wafers: w1 - w5, w7 - w14, w16 - w23, w25 - w26

Wafer flat:

The wafer flat is pointing upwards in the furnace boat

Results

The thickness of the deposited phosphorous doped polySi layer has been measured in five point over each wafer using the Ellipmeter.

Ellipsometer measurements of the phosphorous doped polySi thickness
Test wafer number		w6	w15	w24
Ellipsometer measurement points (x [cm], y [cm]) and thickness
	(0,0) Center point	102.5 nm	98.6 nm	96.2 nm
	(-4,0)	111.6 nm	105.0 nm	104.0 nm
	(0,4) Wafer flat	115.9 nm	106.7 nm	103.1 nm
	(-4,0)	110.9 nm	105.2 nm	105.6 nm
	(-4,0)	102.5 nm	100.5 nm	101.3 nm
Average thickness		109 nm	103 nm	102 nm

Thickness # 3 in nm vs. Position X (cm) Y (cm) Z 0 0 102,47805 -4 0 111,640358 0 4 115,85836 4 0 110,881874 0 -4 102,468773

Average: 109 nm

The Boron concentration of the film was controlled by the flow of B₂H₆ gas. To establish how boron doping concentration varied with B₂H₆ flow, films of silicon were deposited with B₂H₆ gas flows modulated during deposition to produce doping spikes. The two figures below show a typical SIMS concentration depth profile of a B₂H₆ modulation-doped film deposited on a Silicon dioxide substrate. During deposition, the gas flow of SiH₄ was held constant, while flows of B₂H₆ was varied to create the dopant spikes.

Boron-doped amorphous silicon by using 4" LPCVD polysilicon furnace (B4)

Result from Trine Holm Christensen, @Space, Feb. 2015

Process parameters

The test was made on a n-type silicon wafer (100) with a 110 nm grown thermal oxide)

Pressure: 250 mtorr

Temperature: 580 °C

Silane (SiH₄) flow: 80 sccm

Diborane (B₂H₆) flow: 7 sccm

Time: 75 min

Anneal: @950°C for 60 min in N₂

Test wafer position: Center of the boat

A better uniformity of the resistivity across the wafer was achieved by subsequently annealing in N₂, the annealing was done in Anneal Oxide Furnace (C1). The measured film thickness was 370 nm and the sheet resistance was measured to 200 Ω/sq +/- 15 Ω/sq.