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.