Specific Process Knowledge/Etch/Etching of Silicon/Si etch using RIE1 or RIE2/Specific Process Knowledge/Etch/Etching of Silicon/Si etch using RIE1 or RIE2/RIE1 Travka results

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RIE1 Travka results - Silicon etch rate and profile as function of etch load

Purpose

The purpose of the RIE1 Travka experiments is to measure the silicon etch rate and profile as function of the etch load, i.e. of the percentage of the wafer that is etched.

Experiment

Seven silicon wafers have been etched in RIE1 using the "OH_polyA" recipe. The wafers have been etched in June 2012.

All wafers have the same resist pattern ("Travka" masks), but the etch load differs from wafer to wafer. A description of the process flow is show in the table below. For more information about the "Travka" masks see Travka masks.

Measurements

After the etching the wafers have been cleaved, and trechnes with different mask widths have been inspected with SEM in order to measure resist etch rate, the Si etch depth, the underetch and the trench width. From the Si etch depth the Si etch rate has been calculated.

The resist thickness has been measured on the Filmtek before and after the RIE etching, and thus the resist etch rate is calculted.

Process flow and parameters

Photolithography	Resist thickness	1.5 µm
	Resist masks and etch loads	"Travka5", etch load 5% "Travka10", etch load 10% "Travka20", etch load 20% "Travka35", etch load 35% "Travka50", etch load 50% "Travka65", etch load 65% "Travka80", etch load 80%
Measure resist thickness	Filmtek parameters	Recipe: "RIE_Travka_2points" Points: (x,y) = (10,10);(-10,-10)
RIE preconditioning	Before preconditioning	Check that the "Clean20" recipe has been run
	RIE1 preconditioning parameters	Wafer: dummy wafer Recipe: "RIETrav" (same settings as the "OH_polyA" recipe) Time: 8 minutes
RIE etching	Before etching	Remove native oxide in BHF
	RIE1 etching parameters	Recipe: "RIETrav" (same settings as the "OH_polyA" recipe) Time: 8 minutes
	Note	Etch all wafers the same day
Measure resist thickness	Filmtek parameters	Recipe: "RIE_Travka_2points" Points: (x,y) = (10,10);(-10,-10)
SEM characterization	Note	Cleave wafers at ARDE lines (lower right corner towards the flat)
	Mask trench widths to be measured	2 µm 4 µm 10 µm 50 µm 200 µm
	Measurements	Trench width Si etch depth Si etch angle Underetch

Results

RIE1 Travka results

Silicon etch rate as function

• Result of InP etching. David Larsson, DTU Photonics, 2011
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A table with the etching result can be found here:

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Mask	Resist etch rate [nm/min]	Silicon etch rate [µm/min]					Trench width [µm]					Under etch [µm]					Silicon etch angle [oC]
		2 µm	4 µm	10 µm	50 µm	200 µm	2 µm	4 µm	10 µm	50 µm	200 µm	2 µm	4 µm	10 µm	50 µm	200 µm	2 µm	4 µm	10 µm	50 µm	200 µm
Travka5	67.31	0.6	0.63	0.63	0.62	0.61	2.60	4,91	10.96	51.00	201.90
Travka10	63.94	0.57	0.59	0.59	0.58	0.61	2.32	4.60
Travka20	63.13	0.63	0.63	0.64	0.64	0.59
Travka35	59.63	0.57	0.60	0.61	0.61	0.55
Travka50	57.13	0.47	0.5	0.51	0.51	0.49
Travka65	57.88	0.41	0.41	0.42	0.42	0.43
Travka80	57.56	0.37	0.36	0.37	0.37	0.38
Common	Temperature 20 degs, HBC 10 torr, Short funnel, with baffle & 5mm spacers