Plasma Asher 4

Product name: PVA Tepla Gigabatch 380M
Year of purchase: 2024

Descum of AZ 5214E on 100 mm wafers. The descum process development was done for a single substrate, as well as 3 substrates (for decreased ashing rate and improved ashing uniformity). The substrates were placed vertically in the glass boat.

Single vertical substrate
3 vertical substrates:
Dummy - Test - Dummy

For the 3 substrates only the center substrate was used for testing, the front and back wafers were used as dummy wafers. The wafers were placed in consecutive slots - when running multiple wafers in this way, the first and last wafers should always be dummy wafers.

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Typical descum parameters
Tested with 1.5 µm AZ 5214E on 100 mm silicon substrate.

O₂: 100 sccm
N₂: 100 sccm
Pressure (DSC): 1.3 mbar
Power: 200 W
Chamber temperature at start (with door closed): 30°C
Time (single wafer): 5-10 minutes = 35-72 nm ashed
Time (multiple wafers): 10-15 minutes = 40-80 nm ashed

	Single substrate	Center of 3 substrates
Test results: ashing rate	5.7 ±2.1 nm/min	3.8 ±1.6 nm/min
Test results: non-uniformity	0.6 ±0.4%	0.4 ±0.2%
Wafers	1	3
Wafer size	100 mm	100 mm
Boat position	Center of chamber	Center of chamber
Test wafer position	Center of boat	Center of boat
Total gas flow rate	200 sccm	200 sccm
Gas mix ratio	50% N₂	50% N₂
Chamber pressure	1.3 mbar	1.3 mbar
Power	200 W	200 W
Test processing time	Tested parameter	Tested parameter
Test average temperature	33°C	33°C

Single wafer descum ashing rate and uniformity for plasma asher 4 & 5

Ashing amount and ashing rate when processing a single 100 mm wafer.

Ashing amount and rate
Ashing time [min]:	1	2	5	10	15
Ashing amount [nm]:	5.2	6.2	35.1	72.3	87.1
Ashing rate [nm/min]:	5.2	3.1	7.0	7.2	5.8

Ashing non-uniformity
Ashing time [min]:	1	2	5	10	15
Pre-descum film thickness range [nm]:	11	12	10	11	9
Pre-descum non-uniformity [%]:	0.37	0.40	0.33	0.37	0.30
Post-descum film thickness range [nm]:	10	10	12	19	33
Post-descum non-uniformity [%]:	0.33	0.33	0.41	0.66	1.18

Multi wafer descum ashing rate and uniformity for plasma asher 4 & 5

Ashing amount and ashing rate when processing multiple 100 mm wafers. Test measured on the center of 3 wafers.

Ashing amount and rate
Ashing time [min]:	1	2	5	10	15
Ashing amount [nm]:	4.3	6.7	10.1	39.5	78.8
Ashing rate [nm/min]:	4.3	3.4	2.0	4.0	5.3

Ashing non-uniformity
Ashing time [min]:	1	2	5	10	15
Pre-descum film thickness range [nm]:	11	13	11	12	14
Pre-descum non-uniformity [%]:	0.37	0.43	0.37	0.40	0.46
Post-descum film thickness range [nm]:	11	9	10	12	21
Post-descum non-uniformity [%]:	0.37	0.30	0.33	0.41	0.74

Comparison between single substrate processing and multi substrate processing for plasma asher 4 & 5

Processing a single substrate using the standard descum settings will provide users with a relatively controllable and uniform process. Adding dummy substrates in close proximity with the process substrate will reduce the ashing rate and improve the uniformity:

Ashing amount
Ashing rate
Non-uniformity

Comparison of ashing rate between substrate sizes

It is assumed that the low power descum rates, for different substrate sizes, follows the same pattern as the high power ashing rates, which can be seen here.