Revision as of 10:23, 31 May 2016

Modification of showerhead in december 2014

The showerhead that distributes the process gasses inside the plasma source was changed. In the old design, the showerhead had a number of 300 µm holes intended to distribute the gas uniformly inside the plasma source. The passage through the holes had a flow resistance that would cause the gasses coming from the MFC in a Bosch process to get mixed up - in this way working against the separation of the etch and dep cycles. In the new design the gas flow resistance has been reduced by using 1 mm holes in the showerhead instead. 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.

Comparison of continuous processes

Black silicon recipe

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
Continuous black silicon recipe on blank wafer		S003900	Wafer edge		S004679	Wafer edge

Comparison of switched processes

Process A

Recipe	Name	Temp.	Deposition step						Etch step							Comments
Recipe	Name	Temp.	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	20	4	25	200	0	0	2000	7.0	25(1.5s) 150	0	350(1.5s) 550	5	2800	140(1.5s) 45	Old	1
	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	20	4	25	200	0	0	2000	7.0	25(1.5s) 150	0	350(1.5s) 550	5	2800	140(1.5s) 45	New	1	Profile improved

SOI

Recipe	Name	Temp.	Deposition step						Etch step							Comments
Recipe	Name	Temp.	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
Recipe	Name	Temp.	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
Recipe description	Name	Temp.	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

@@ Line 1: / Line 1: @@
 = Modification of showerhead in december 2014 =
-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.
+The showerhead that distributes the process gasses inside the plasma source was changed. In the old design, the showerhead had a number of 300 µm holes intended to distribute the gas uniformly inside the plasma source. The passage through the holes had a flow resistance that would cause the gasses coming from the MFC in a Bosch process to get mixed up - in this way working against the separation of the etch and dep cycles. In the new design the gas flow resistance has been reduced by using 1 mm holes in the showerhead instead. 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 [[Specific Process Knowledge/Etch/DRIE-Pegasus/processC|Process C]], [[Specific Process Knowledge/Etch/DRIE-Pegasus/nanoetch/nano142|Nano1.42]], isotropic etches, barc etches or the black silicon recipes are not believed to be noticeably affected.