The furnace A4 phosphorus predep(N-predep) can be used to predeposit silicon wafers with phosphor. The silicon wafers are positioned in a quarts boat. Phosphor is predeposited in the silicon wafers.

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Test of Phosphorus Predep furnace

Purpose

To study the coherence between the temperature of the Predep and dive-in for doping with phosphorus in DTU-Danchip Phosphorus Predep furnace (A4).

Experiment setup

There was used 20 boron doped wafers (p-type). There was used four wafer to the five different temperature. There was five dummy wafers on each side of the test wafers. The dummy wafer nearest to the test wafers was changed in between the runes so doping from a dummy wafer was minimized.

Run #	Temperature	Process time with POCl₃	Anneal time in N₂	Wafer #
1	850 ^oC	15 minutes	20 miuntes	1, 2, 3, 4
2	900 ^oC	15 minutes	20 miuntes	5, 6, 7, 8
3	950 ^oC	15 minutes	20 miuntes	9, 10, 11, 12
4	1000 ^oC	15 minutes	20 miuntes	13, 14, 15, 16
5	1050 ^oC	15 minutes	20 miuntes	17, 18, 19, 20

After the Predep was two wafer from each run taken out to be further processed. The wafers was 1, 2, 5, 6, 9, 10, 13, 14, 17, 18.

These wafers was dipped in BHF to get the phosphorus glass layer of before the Drive-in process. The Drive-in process was made in Danchip Phosphorus Drive-in furnace (A3). There was a dummy wafer in between the wafers from different temperatures so doping from wafer to wafer was minimized. The Drive-in was done with the process "DRY1050" with is a dry oxidation at 1050 ^oC for 100 minutes and 20 minutes annealing. At the oxdation was the O₂ flow was 5 SLM and N₂ flow for annealing was 3 SLM.

Test measurement

There was made several measurement on the different wafer in the process. After the Predep was the Phosphorus glass layer thickness measured and the sheet resistance and slice resistivity measured on the same after a BHF etch.

**Measurement after Predep**
	Elipsometer		Four Point Probe
Wafer #	Thinkness [nm]	Refrative index	Sheet resistance [Ω_sq]	Slice Resistivity [Ωcm]
3	27,4	1,4623	311	17,32
7	45,27	1,4622	138,5	7,61
11	61,36	1,4625	16,12	0,859
15	80,45	1,4624	7,4	0,392
19	119,37	1,4623	6,6	0,246

**Measurement after Drive-in**
	Avg. five point on Filmtek		Four Point Probe
Wafer #	Thinkness [nm]	Refrative index	Sheet resistance [Ω_sq]	Slice Resistivity [Ωcm]
2	110,436	1,46536	189,7	13,06
6	116,284	1,46288	101,6	5,32
9	137,06	1,4604	10,05	0,527
14	141,456	1,46508	4,72	0,216
18	139,872	1,46586	3,23	0,165
Test	110,7118	1,46286	-	-