Page 164 - Semiconductor Manufacturing Handbook

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PLASMA ETCHING

4 1

3
Etch rate (µm/min) 2 0.5

0.75 Scallop length (µm)
1 Fixed duty cycle = 50% 0.25

0 0
0 2 4 6 8 10 12
Cycle time (sec)
FIGURE 12.9 The overall TDM etch rate (left axis) and scallop length
(right axis) when the duty cycle of etch/deposition steps is fixed at 50 percent.
Scallop dimension is reduced with the retaining of a high etch rate.

120%
D : Polymer D : Polymer thickness
0
1
thickness on at trench bottom
trench top
100% Polymer
Mask
80%
Silicon
D 1 /D 0 60%
40% 22.5 mT
18.0 mT
20% 15.4 mT

0%
0.00 1.00 2.00 3.00 4.00 5.00 6.00
Aspect ratio
(a)
15 RIE bias = 500 V
Passivation removal rate (nm/s) 9 6
12

0 3
0.00 1.00 2.00 3.00 4.00 5.00
Trench width (µm)
(b)
FIGURE 12.10 Measurements on polymer deposition and removal
rates as functions of aspect ratio: (a) polymer thickness in the trench bot-
tom is normalized to that on the resist mask surface, and (b) polymer
removal rate at the trench bottom is measured.

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