| 1 |
If
the wafer surface is directly chucked by electrostatic chuck without surface
protection tape, will SF6 plasma etch the active surface of wafer?
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Moreover,
the good contact between chuck and wafer as well as the
He gas flow prevent etching species (F radicals and ions) to get to the wafer
front side. Consequently it is not possible to find etching on the wafer front
side.
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| 2 |
Regarding
moat etch, please advice the max. depth and aspect ratio? |
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As
to moat etching: the result depends upon the gas you used and the mask. We
managed on 200mm, with Fluorine gas, you may easily achieve an aspect
ratio of 3:1, with Chlorine, the ratio should be 6:1 or even more.
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| 3 |
Why
the etch rate is higher for structured wafer?
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This
high etch rate comes from an intelligent combination of microwave and
radio frequency energy as it is described in the technical description. It
requires, however, high gas flow (3 liters / min for a 200mm wafer) since
the theoretical amount of F-containing gas (SF6) is 1.5 l/min for forming
SiF4 form Si and SF6 at an etch rate of 25 µm/min for a 200 blank
wafer.
So,
it will be understood that if this energy and the high amount of R-radical
and F+-ion can be concentrated to the 30 - 70 cm2 only of the open
structures of a 200 mm wafer relative to the ~ 300 cm2 of a blank wafer,
the etch rate will go up strongly.
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| 4 |
How
to measure the temperature on the electrostatic chuck or at the wafer surface
during etching process?
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Temperature
can be measured by Pyrometer.
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| 5 |
What
is the actual
pressure conditions inside the XPL-900 etch module during the etch process?
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Pressure:
0.8 - 1.5 mbar. Gas used for 200mm Si wafers: SF6 is 3 slm
(standard liters per minute) and N2O is 1.5 slm.
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| 6 |
Regarding
the XPL-900
wafer handling: Does the electrostatic chuck /end piece have any negative
impact on the wafer quality/functionality? How is it that the electrostatic
chuck / end piece allows safe wafer handling?
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The
electrostatic chuck has 700 - 800 Vdc. All tests indicated no damage of or
measurable influence on chips. We undertook the Charm-II charge monitoring test
wafer for Voltage, current induced and UV radiation exposure tests from
WCM, all results show positive.
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| 7 |
Can
Secon Etcher etch on SiO2 with resist mask?
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SiO2
can not be etched with photoresist mask. We would need a hard mask like Ni
or Al.
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| 8 |
Can
Secon Etcher handled taped wafer? |
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If the tape can resist up to 120 ºC, it will not be attacked by the
process. But the bigger problem is caused by the glue: Nearly every glue
contains solvent. When the taped wafer is put in the machine, the solvent
causes bubbles between tape and wafer due to the vacuum. These bubbles
entail first, that there is no more good thermal contact of the wafer with
the water cooled electrode, and second, when the RF is switched on, there
is a secondary plasma in the bubbles, that will damage the wafer
frontside.
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| 9 |
Can
XPL-900 system upgradeable from 8" wafer to 12" wafer? |
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System
upgrade from 8" platform to 12" is possible only if the basic
equipment is a 12" equipment platform, which means an 8" unit +
approximately 30%. Such 12" equipment can used for 8" wafers as
well. Time requested for equipment change from one wafer size to another
is about 1/2 day. What has to be changed is the electrostatic chuck of the
lower electrode (each wafer size requires a special electrostatic chuck.),
the ceramic housing of the lower electrode and the electrostatic end piece
of the transport arm.
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| 10 |
What
is the etching process gas consumption? |
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Gases
for etch process are SF6 and N2O. Gas consumption is
- 3000
sccm SF6 + 1500 sccm N2O for 200 mm wafer
- 7000
sccm SF6 + 3500 sccm N2O for 300 mm wafer
Note:
sccm = standard cubic centimeter or milliliter per minute
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| 11 |
What
is the composition and quantity of exhaust gases to be purged out to gas
scrubber? and what is the preparation in the scrubber in order to treat
this exhaust gases? |
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Amount
of exhaust gas is process gas + solid silicon converted to SiF4 gas +
nitrogen purge of vacuum pump. This is approx. (total amount of process
gases) times 4. These exhaust gases should go to a scrubber.
.............to be explained
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| 12 |
What
is the life spend for the electrode? |
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Secon
guarantee min 50,000 wafers operation.
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| 13 |
Does
Secon apply any on-line monitoring system for the etching process? |
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Monitoring
system of the dry etching process can be done as an option, a thickness
monitor on laser basis. Standard operation is controlled by time. Silicon
removal goes linear with time, etch rate is constant.
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| 14 |
What
are the consumables spare parts? |
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Consumables
can be replaced easily. The consumables are viewing ports, ceramic
insulators and magnetrons of the microwave radical generator.
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| 15 |
If
the system stops by emergency situation, how does the interlock system
work? What happens to the wafer which is still under etching chamber? Is
it possible to survive those wafers? |
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In
case of an emergency situation and equipment shut down the valves and
interlock will go in safe positions. Supply of gas is stopped since
all gas valves are closed without power. Vacuum valves between process
chamber and pump will be closed. The wafer will stay under vacuum waiting
for finishing of etch process. The computer will tell how much time left
to complete the etching process, but not start automatically. The operator
must restart and continue the process after error message resolved. The
wafer will survive.
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| 16 |
What
is the minimum voltage required to hold the 8' wafer? |
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The
voltage depends on the He backside pressure (for wafer cooling). Secon use
850V in the 10 mbar He pressure range. This He pressure is measured and
controlled in the He gas line, ~ 30 - 50 cm down from the chuck.
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| 17 |
What
is the function of Nitrogen gas in XPL-900 etcher? |
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Nitrogen
is used as purging gas and cooling gas.
- Purging
gas: After completing the etching process, the purge N2 gas
was used to clean the gases (SF6, N2O, SO2,
SiF4 and N2) in the chamber.
- Cooling
gas: Cooling gas gets into the stainless steel tube (antenna) of
traveling wave rod and comes back between SS tube and alumina
insulator. It is for traveling wave rod cooling.
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