Marvell NanoLab
Member login
Lab Manual Contents
MercuryWeb
Berkeley Microlab
Chapter 7.2
Technics C Plasma Etching System
(technics-c - 584)
1.0
T it l e
Technics C Plasma Etching System
2.0
Pu rp o s e
Technics C is a plasma etching system used for descumming/ashing of photoresist and nitride etching.
3.0
S co p e
This document describes the general operation of Technics C. Technics C Plasma Etcher is primarily
for descumming and ashing photoresist. It is also used for nitride etching. Technics C contains module
PE II-A and module PD II-A. Module PE II-A comprises the etch chamber, R.F. supply with power
adjustment and vacuum system. Module PD II-A comprises the platen temperature controller, which is
not being used, and gas supply switches. The chamber accommodates multiple 4” wafers or a single 6”
wafer. This system may be used in manual mode.
4. 0
Ap p l i ca b l e Do cu m en t s
Revision History
5. 0
Def in it io n s & Pr o c e s s T e rm in o lo g y
5.1
Oxygen (O2): a process gas used in descumming, ashing photoresist and chamber cleaning.
5.2
Helium (He): a process gas used in etching.
5.3
Sulphur hexafluoride (SF6): a process gas used in etching.
6.0
S af et y
Pay particular attention to the instructions pertaining to vacuum/vent procedures as the vacuum pump
may be damaged.
7. 0
St at i st ic al / P ro c e s s D at a
Pertinent information can be found in the following locations:
8. 0
7.1
Problem and comments section under equipment section of Merucry.
7.2
Enable message for Technics C.
Av ai l ab l e P ro c es s es , G a s es , P ro c es s No t e s
8.1 Available Processes
8.1.1 Oxygen Scourge
Use this procedure to clean the chamber before doing any SF6 nitride etching.
Settings:
Gas:
O2 (Gas #1, PE module)
Flow:
No MFC control
Power:
300 Watts
Pressure:
180-190 mTorr
technics-c
Chapter 7.2
Time:
20- 30 min.
8.1.2
Descum
This is used after developing exposed photoresist, before hard baking, to eliminate any
residual scum, which may be present.
Settings:
Gas:
O2 (Gas #1, PE module)
Flow:
No MFC control
Power:
50 Watts
Pressure:
180-190 mTorr
Time:
1 min.
8.1.3
Resist Stripping or Ashing
For complete removal of standard hard baked G and I-line photoresist.
Settings:
Gas:
O2 (Gas #1, PE module)
Flow:
No MFC control
Power:
300 Watts
Pressure:
180 - 190 mTorr
Time:
7 min.
8.1.4
Nitride Etch
Before doing any nitride etching, it is recommended that you do an oxygen scourge (see
Section 8.1.1). The scourge is important to guarantee uniform and repeatable nitride etch
rates.
Settings:
Gases:
SF6 (Gas #2, channel 2 on PD module)
He (Gas #2, channel 3 on PD module)
Flow:
SF6 - 13.0
He - 21.0
Power:
100 Watts
Etch Rate:
Nitride: 500 A - 600 A/min.
Oxide: 200 A – 300 A/min.
Beware! This etch recipe will consume single crystal Si at the rate of approximately
8000A/min.
It is suggested that you approximate the time you will need to etch through your nitride
film, run your sample for half the total time, open the chamber and rotate your wafers
around their central axes by 180 degrees, and then etch again. This provides more
uniformity in etching. Remember that the etch rate will vary with the amount of area to be
etched.
Note: Formerly, nitride was etched at 50 watts. At this power it may be difficult to obtain
a uniform result.
8.2
Available Gases
► O2
► SF6
► He
The O2 is used primarily for plasma ashing/descumming photoresist, while the other gases are
for etching nitride.
-2-
technics-c
Chapter 7.2
Note: Please do not adjust gas knobs on the black box connected to the VENT TOGGLE VALVE.
9. 0
Eq u ip m en t O p e r at io n
The following is a detailed outline of the general procedure to follow in using Technics-C.
9.1
9.2
Precautions and Hints
9.1.1 Always leave the PD and PE II-A power on when finished.
9.1.2
Always leave the vent on when you begin a pump down -- switch vent off after 2-3
seconds. This will sweep the oil that has collected at the hose end near the chamber
back toward the mechanical pump. (Note: The SOL'N should always be OFF when you
vent the chamber, but VENT should always be on when you begin to pump down the
chamber.)
9.1.3
Always leave the vent on when the chamber is open.
Starting Up
9.2.1 Check the status of the controls on the front of the machine. It should be in the following
condition:
PEIIA
PDIIA and MFC unit
Parameter
Setting
Parameter
Setting
Main Power
ON
Main Power
ON
Mode
Manual
Heater
OFF
Solenoid
Closed
Flow controllers
OFF
Vent Switch
Open
RF Power Switch
OFF
RF Power
Fully
counterclockwise (0)
Gas 1
OFF
Gas 2
OFF
9.2.2
Once everything checks out, enable through the Mercury (technics-c).
9.2.3
If you are going to etch nitride, it is advised that you carry out an oxygen scourge of the
system to clean it before introducing your sample. If so, refer to Section 8.1 before
proceeding.
9.2.4
When you are ready to introduce your sample, vent the chamber by toggling the VENT
ON (DOWN) valve on the side of PEII-A unit (See figure 2). Be sure that the solenoid
(SOLN) on the vacuum line is closed when you do this. It will take about 15 seconds for
the chamber to fill.
9.2.5
Once it is at atmospheric pressure (Pressure gauge is a gray box next to the PEII-A unit),
open it carefully -- the top is very heavy -- and place your wafers on the plate. Close the
top carefully, being sure not to allow it to fall.
All gases are connected through Gas #2 on the main PE module, except O2 for O2
scourge, descum resist and ash resist. This port will flow the gases as indicated on the
PD gas control panel:
(1) SF6 (13.0 sccm);
(2) He (21.0 sccm); and
-3-
technics-c
Chapter 7.2
(3) O2 (10 sccm). Gas correction factors and set points on the PD module are set
according to the gases and processes selected.
The gas correction values are set as follows:
O2 = 1.00
SF6 = 0.28
He = 1.46
Flow rates for O2 plasma processing and standard nitride etching should be set as
indicated above.
9.3
Running the System - Manual
9.3.1 You are now ready to start the vacuum pump. Always leave Vent Switch ON. Leaving
the VENT toggle valve ON DOWN (See figure 2) on the side of the PEII-A unit, toggle the
SOL’N (vacuum pump) switch open. After 2-3 seconds, close the VENT toggle valve
VENT OFF UP (See Figure 2) to allow the pump to lower the pressure of the chamber.
9.3.2
You can watch the pressure drop as the system comes under vacuum. When the system
reaches ~30 mtorr, you can introduce the gas you wish to use into the chamber by
toggling the appropriate gas switches as follows:
9.3.2.1 Process 1 for O2 scourge, descum resist or strip resist: Flip gas #1 switch up
(open) on PEII-A module. The pressure in the chamber will rise as gas flows in,
and then stabilize. If the pressure is not at a desirable level, adjust it with the
black knob next to gas #1 switch (See figure 1).
9.3.2.2 Process 2 for nitride etch, flip the appropriate toggle switch on the PD module to
the up (open) position. The green light will go on. The gas flow can be verified by
switching to the proper channel. Then open the GAS #2 switch (See figure 1) on
the PE module. The pressure in the chamber will rise as gas flows in, and then
stabilize.
9.4
9.3.3
Once flow into the chamber is stable and at the desired pressure, you can strike a
plasma by switching the power toggle on and turning the dial clockwise until the desired
power is reached. You can see the plasma through the window on the front of the
chamber. Begin timing your run.
9.3.4
Once the run is complete, turn off the power first. ALWAYS turn off the power before
turning off the gas.
9.3.5
If process 1 was done, then switch off GAS #1 and allow the chamber to pump down to
~30 mtorr so you can be sure all gases have been swept out of the chamber. If process
2 was done, then turn off the gases on the PD module first, and let the vacuum pump
pump out the gas line for a few seconds. Then close off the GAS #2 switch and allow the
chamber to pump down to ~30 mtorr so you can be sure all gases have been swept out
of the chamber.
9.3.6
Turn off the vacuum pump by switching the SOL’N toggle to the closed position. Now you
may vent the chamber by switching the VENT toggle valve ON (DOWN) on the side of
the PEII-A unit.
9.3.7
The chamber pressure will now come up to atmosphere and you may remove your
sample.
Restoring the System to Standby
9.4.1
Once your sample has been removed, close the chamber and start the SOL’N vacuum
with the vent toggle valve ON (DOWN). After a couple of seconds, close the vent toggle
valve OFF (UP) and allow the chamber to pump down to ~35 mtorr. Close the SOL’N
switch. Be sure that gas switches and power are off.
-4-
technics-c
Chapter 7.2
9.4.2
Disable the system on the Mercury.
10 T ro u b l e sh o o t in g G u i d e s
11 F ig u r es & Sc h e m a t i c s
Technics PE II-A
-5-
technics-c
Chapter 7.2
Figure 1
Figure 2
Technics PD II-A
-6-
technics-c
Chapter 7.2
K. Chan - October 2002
K. Chan – Revised May 2012
-7-