Specific Process Knowledge/Etch/DRIE-Pegasus/showerheadchange

Comparison of continuous processes

The showerhead that distributes the process gasses inside the plasma source has been changed. With the new design the gas flow resistance in the gas line from MFC to plasma has been reduced. This has very little or no impact on processes that have a continuous gas flow - i.e. processes that are not switched. However, for processes with several gas flows that switch on and off, the switching from one gas flow to another will be much more well defined. This enables us to run Bosch processes with shorter cycles times. Shorter cycles times means smaller scallops and hence lower roughness and better control.

As stated, we believe that only switched processes will be affected by this change. Continuous processes such as Process C, Nano1.42, isotropic etches, barc etches or the black silicon recipes are not believed to be noticeably affected.

Process		Before (Old showerhead)			After (New showerhead)
Name/Type	Description/parameters	Wafer ID	Comment	SEM images	Wafer ID	Comment	SEM images
Continuous black silicon recipe on blank wafer	15 mins, -10 degrees, 32 mtorr, 60 sccm SF6, 55 sccm O2, 70 W platen	S004592	Wafer centre		S004679	Wafer centre
		S003900	Wafer edge		S004679	Wafer edge
Continuous isotropic silicon etch called isoslow7	1 minute, 10 degrees, 10 mTorr, 80 SF6, 150 W coil, 3 W platen	S003900	4" wafer, 50 % load		S00XXX	No test yet	File:S00XX centre.jpg

Comparison of switched processes

Process A

Recipe	Name	Temp.	Deposition step						Etch step							Comments
			Time	Pres.	C4F8	SF6	O2	Coil	Time	Pres.	C4F8	SF6	O2	Coil	Platen	Showerhead	Runs	Key words
Process A	Step1 11 cyc	20	4	25	200	0	0	2000	7.0	25(1.5s) 90>>150	0	350(1.5s) 550	5	2800	120>>140(1.5s) 45	Old	1
	Step2 44 cyc		4	25	200	0	0	2000	7.0	25(1.5s) 150	0	350(1.5s) 550	5	2800	140(1.5s) 45
	Step1 11 cyc	20	4	25	200	0	0	2000	7.0	25(1.5s) 90>>150	0	350(1.5s) 550	5	2800	120>>140(1.5s) 45	New	1	Profile improved
	Step2 44 cyc		4	25	200	0	0	2000	7.0	25(1.5s) 150	0	350(1.5s) 550	5	2800	140(1.5s) 45

SOI

Recipe	Name	Temp.	Deposition step						Etch step							Comments
			Time	Pres.	C4F8	SF6	O2	Coil	Time	Pres.	C4F8	SF6	O2	Coil	Platen	Showerhead	Runs	Key words
SOI etch	SOI	20	2	25	250	0	0	2000	3	30	0	400	40	2800	75 (0.025s, 75%)	Old	1
	SOI	20	2	25	250	0	0	2000	3	30	0	400	40	2800	75 (0.025s, 75%)	New	1	OK

Process D

Recipe	Name	Temp.	Deposition step						Etch step							Comments
			Time	Pres.	C4F8	SF6	O2	Coil	Time	Pres.	C4F8	SF6	O2	Coil	Platen	Showerhead	Runs	Key words
Process D	Original	0	2	20	150	0	0	2000	2.4	26	0	275	5	2500	35	Old	1
	Original	0	2	20	150	0	0	2000	2.4	26	0	275	5	2500	35	New	1
	New Process D	0	1	20	150	0	0	2000	3	26	0	275	5	2500	35	New	4	Large undercut
	PrD01	0	1	20	150	0	0	2000	2.4	26	0	275	5	2500	35	New	2
	PrD02	0	1.1	20	150	0	0	2000	2.4	26	0	275	5	2500	35	New	1
	PrD-3	0	1	20	150	0	0	2000	2.5	26	0	275	5	2500	35	New	1
	PrD-4	0	1	20	150	0	0	2000	2.2	26	0	275	5	2500	35	New	1	Best one so far!

Polysilicon etch

Recipe description	Name	Temp.	Deposition step						Etch step							Comments
			Time	Pres.	C4F8	SF6	O2	Coil	Time	Pres.	C4F8	SF6	O2	Coil	Platen	Showerhead	Runs	Key words
Polysilicon etch	polySi etch DUV mask	30	2.3	10	50	0	0	600	5.0	10	20	60	5	400	40	Old	1	Slightly over-etching to ensure complete absence of grass
	polySi etch DUV mask	30	2.3	10	50	0	0	600	5.0	10	20	60	5	400	40	New	1
	Cpoly1	30	1.2	10	50	0	0	600	5.0	10	20	60	5	400	40	New	1	Very aggressive, unusable
	Cpoly2	30	1.4	10	50	0	0	600	5.0	10	20	60	5	400	40	New	1
	Cpoly3	30	1.6	10	50	0	0	600	5.0	10	20	60	5	400	40	New	1
	Cpoly4	30	1.8	10	50	0	0	600	5.0	10	20	60	5	400	40	New	1
	Cpoly5	30	2.0	10	50	0	0	600	5.0	10	20	60	5	400	40	New	1