Utah-94-721002-System-Manual.pdf - 第149页

System Manual = lñÑçêÇ=fåëíêìãÉåíë=mä~ëã~= qÉÅÜåçäçÖó= mä~ëã~ä~Ä PKOKO= f`m=çéÉê~íáåÖ=é~ê~ãÉíÉê=ê~åÖÉë= For an ICP 180 or ICP 380 the typical process opera ting ranges are: Total gas flows = 10 to 200sccm. The maximum fl…

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For an RIE tool the typical process operating ranges are:

Total gas flows = 10 to 150 sccm. The maximum flow depends on type of pumps fitted to the system i.e.

their maximum flow capacity, their pumping performance, and the required operating pressure. If you

need to use a low pressure, you may have to limit the flow rate to achieve this.

Pressure = 5 to 500mTorr. Below 50mTorr, the plasma may not strike easily (or with sufficient stability)

for certain gases and power levels, so you need to check this and adjust the process accordingly, since

operating the system without a plasma could cause damage. This is because it is likely to cause a high

reflected power, or dumping of power into the matching unit. It is always essential to check for a plasma.

You can use the ‘low pressure strike’ feature in the software to allow easier striking for low pressure

processes. For certain flow/pressure combinations, the pressure controller may have difficulty in

maintaining a constant pressure, therefore this may also be a determining factor in the flow/pressure

used.

RF power = typically 20W to 400W (or up to 1200W for RIE System133 or RIE 800 Plus). A plasma may not

strike easily for low power levels for certain gases. You will need to check this and adjust the process

accordingly, since operating the system without a plasma could cause damage. It is always important to

have a cover plate (typically quartz or graphite) on the RIE electrode to protect it from sputter etch

damage, particularly when operating with high RF powers and therefore high DC biases.

Helium pressure (if applicable) = 0 to 30Torr. Depends on the cooling efficiency required (some

processes benefit from no cooling) and the maximum tolerable helium leakage.

Temperature is limited by the operating range of the electrode or its heater/chiller, depending on type

of electrode or heater/chiller used.

NOTES:

(A) The system base pressure will be approaching 10

-6

Torr when measured using the Penning gauge.

However, the time taken to reach this pressure will depend on whether the chamber has recently

been vented to atmosphere and the cleanliness of the chamber walls. If the process chamber /

electrodes are anodised, the time will increase as the anodised surfaces will take longer to outgas

compared with bare metal surfaces.

(B) Operating with chlorine-based processes can cause damage to the electrode unless it is protected

with a cover plate (or dummy wafer in a tool with wafer clamping).

damage to the matching unit or RF generator. To reduce the high reflected power, adjust the

process parameters or re-tune the matching unit.

Process Information (Information contained in this document is confidential)

Issue 1: December 03 Page 6 of 30 Printed: 08 January 2006 09:37

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For an ICP 180 or ICP 380 the typical process operating ranges are:

Total gas flows = 10 to 200sccm. The maximum flow depends on type of turbo pump, i.e. its maximum

flow capacity, and the required operating pressure. If you need to use a low pressure, you may have to

limit the flow rate to achieve this.

Pressure = 1 to 60mTorr. Below 5mTorr and above 20mTorr the plasma may not strike easily (or with

sufficient stability) for certain gases and power levels, so you need to check this and adjust the process

accordingly, since operating the system without a plasma either on the substrate electrode or in the ICP

tube could cause damage. This is because it is likely to cause a high reflected power, or dumping of power

into matching unit. It is always essential to check for a plasma in both regions. You can use the ‘low

pressure strike’ feature in the software to allow easier striking for low pressure processes. For certain

flow/pressure combinations, the pressure controller may have difficulty in maintaining a constant

pressure, therefore this may also be a determining factor in the flow/pressure used.

ICP power = approximately 200W to 2500W (or 4000W for ICP 380). The minimum power level will be

dependent on how easily the plasma strikes for certain gases. You will need to check this and adjust

process accordingly, since operating system without a plasma either on the substrate electrode or in the

ICP tube could cause damage.

The maximum ICP power limit is set by the power rating of the RF generator. However, most processes

perform well with only moderate ICP power levels. This also helps to avoid excessive substrate heating.

Substrate electrode RF power = typically 5W to 400W. A plasma may not strike easily for low power

levels for certain gases. You will need to check this and adjust the process accordingly, since operating the

system without a plasma either on the substrate electrode or in the ICP tube could cause damage.

Helium pressure = 0 to 30Torr. Depends on the cooling efficiency required (some processes benefit from

no cooling) and the maximum tolerable helium leakage.

Temperature is limited by the operating range of the electrode or its heater/chiller, depending on type

of electrode or heater/chiller used.

NOTES:

(A) The system base pressure will be of approaching 10

-6

Torr or better when measured using the

Penning gauge. However, the time taken to reach this pressure will depend on whether the

chamber has recently been vented to atmosphere and the cleanliness of the chamber walls. If the

process chamber / electrodes are anodised, the time will increase as the anodised surfaces will take

longer to outgas compared with bare metal surfaces.

(B) Operating with chlorine based processes can cause damage to the electrode unless it is protected

with a dummy wafer.

damage to the matching unit or RF generator. To reduce the high-reflected power, adjust the

process parameters or re-tune the matching unit.

Process Information (Information contained in this document is confidential)

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"Low pressure strike" is a necessary software facility, since for low pressure RIE or ICP processes, the

concentration of free electrons being produced simply isn't high enough to start and maintain the

ionisation 'chain reaction' or avalanche which is required to initiate the plasma. So it is necessary to use

higher pressures during the first few seconds of the process step. The software therefore allows the

operator to raise the pressure briefly at the start of the plasma process to enable the plasma to strike.

This does not cause any problems for the processes involved, because the time taken to strike the plasma

at the higher pressure is very short, and will be a very small percentage of the total process time.

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With any plasma etch system it is important to remember that DC bias readings can be affected by surface

coatings on the lower electrode. These can include:

(a) Quartz cover plate (or any other insulating cover plate material),

(b) Electrode surface anodisation,

(d) Any other insulating coating generated by plasma.

In all of these cases, the DC bias reading will be inaccurate due to the lack of DC contact to the plasma.

Quite often, the measured DC bias will be close to zero if there is a complete insulation of the electrode

or if the process conditions are such that there is minimal contact between the exposed areas of the

electrode and the plasma.

This is not to say that the sheath potential (or ion energy) has actually reduced to zero; in fact it has not

changed at all from the non-insulated case. It is simply that the measurement of this value via DC bias is

no longer possible. It is also quite common in these cases for the DC bias reading to vary sharply

throughout the run.

It is therefore recommended that the DC bias for a particular process condition be measured with a bare

electrode (e.g. prior to loading the quartz cover plate). In load locked single wafer systems, it is necessary

to measure the DC bias without a wafer loaded, as this will expose the central wafer lift pin to provide

accurate DC bias measurement.

This is the only way of obtaining a reliable/stable DC bias measurement.

If the electrode is anodised, it may also be necessary to ensure that the wafer lift pin is exposed and clean

as this will be the only conductive path for the DC bias measurement. If there is no wafer lift pin (e.g. RIE

80 Plus), it may be necessary to use the central locating pin for the DC bias measurement or even to

scratch away a small area of anodisation.

If it is suspected that there has been polymer deposition on the electrode, it may be necessary to clean off

the polymer (with an O

plasma or by mechanical cleaning) to allow an accurate measurement of the DC

bias.

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Strongly electronegative mixtures, such as SF

gas above 10 Pa (70 mTorr), may give close-to-zero DC bias.

This is not a fault, but is due to the formation of negative ions in the plasma. A DC bias exists only

because of the difference in mobility between the negative and positive charges in a normal plasma.

When both charge carriers are heavy ions, the plasma does not rectify and the dc bias collapses.

Process Information (Information contained in this document is confidential)

Issue 1: December 03 Page 8 of 30 Printed: 08 January 2006 09:37