ALCATEL ICP-RIE - University of Alberta nanoFAB · NanoFab 08 October 2010 A Micro Machining &...

NanoFab 08 October 2010 A Micro Machining & Nanofabrication Facility

ALCATEL ICP-RIE

LOCATION: Plasma Etch Area

PRIMARY TRAINER: Scott Munro (2-4826, [email protected])

1. OVERVIEW

The Alcatel AMS 110 DE is used for dry etching of dielectric materials, including, but not limited to pyrex, quartz, and SiO2. The system uses a combination of C4F8, Ar, He, CH4 during the etch process. Due to the low selectivity of the process, a hard mask is typically required. At this moment, sputtered metals (Al, Cr) work well for shallow etches, while a thicker metal (plated Ni) or KMPR (thick negative resist) is required for deeper etches. As the Alcatel etcher is still in development mode, please contact Scott or other Nanofab staff for details on processing.

NanoFab, University of Albertawww.nanofab.ualberta.ca

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2. SAFETY PRECAUTIONS

Wafers must be round, 100mm in diameter, and must have a main wafer flat due to the hardware setup on the tool. Smaller pieces may be mounted on a carrier wafer with photoresist, a thin layer of vacuum grease or etch-resistant, vacuum compatible tape (kapton or a thermal release tape are available). If pieces are to be mounted, make sure that there is limited exposure of the tape to the plasma.

The Alcatel uses advanced software, and will stop processing if one or more etch parameters becomes out of tolerance. Users are not allowed to circumvent these set tolerances.

Reflected power occurs when power is not fully transferred from the source to the plasma. A set of capacitors automatically adjust to minimize the reflected power. Running the plasma for an extended time with high reflected power may permanently damage the system. If the capacitors fail to minimize the reflected power and remains consistently above 10% the RF power, stop processing immediately, and contact NanoFab staff.

The Alcatel uses strong electric and magnetic fields; users who wear pacemakers should keep their distance from the tool.

If you are bringing any new materials into the NanoFab for use in your process, it is necessary to fill out a chemical import form (available on our website, http://www.nanofab.ualberta.ca) and supply an MSDS data sheet to Stephanie Bozic.

3. PROCESS COMPONENTS OR FEATURES

Extensive O2 plasma cleaning is performed on the Alcatel in an attempt to keep the chamber clean. The glass etch process uses C4F8 as a source of fluoride ions and radicals, which are used during the etching and forms a difficult to remove polymer, similar to teflon, on any surface not heated or physically etched. The maximum recommended time for any etch step is 10 minutes before performing a 10 minute O2 plasma clean step. Etching longer than 10 minutes without cleaning will most likely cause excessive polymer build up, and will begin to flake off, contaminating the chamber and your sample. The cleaning step is written into most recipes, please do not remove this step.

Wafers should be prepared with an etch mask appropriate to withstand the duration of the etch. For shallow etches, a thin metal mask may be suitable. Positive resists such as HPR504 and AZP4620 are not allowed at this time due to clamp incompatability issues. For deeper etches, a hard mask, such as electroplated Ni or a thick layer of KMPR may be required. If using a KMPR mask, the wafer should be hard baked for an extended period prior to etching.

Post-etch removal of the masking material may be difficult. Plated Ni can be removed in a wet metal etch (ferric chloride), followed by the necessary metal etch used for seed layers. KMPR can be removed in Remover PG or piranha, followed by an O2 plasma clean.

Please contact the appropriate trainers if interested in the above processes.


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4. OPERATING INSTRUCTIONS

4.1 The system operating software should be running. Click the Login button on the bottom left hand corner, enter your username and password, and press OK.

4.2 The chamber will require pre-cleaning prior to etching your wafers. Press the Recipes Edit button on the bottom toolbar to access a list of the available recipes.

Recipes Edit Window

4.3 The window labeled Recipe List contains a list of the standard process recipes, each made up of various steps. Click on the desired recipe to highlight the cell. The display window just below the Recipe List window contains the steps of that recipe.


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Recipes Edit

Current Recipes

HighlightedRecipe

Available Steps

Steps in Highlighted Recipe

Cleaning Recipe

Cleaning Recipe Library


4.4 A 1 minute chamber clean with no wafer should be the first recipe ran. This recipe is labeled Pre-Chamber Clean; select this recipe and in the Recipe List window, select the Clean step. Press Modify to view the process information, and enter in a 1 minute for process time. Select Next to open a second confirmation window, then press OK.

Modify Recipe Window


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Process Time

Power Selection

Gas Flows

Supplied Wattage

Pressure (valve position or abs pressure)

He cooling pressure


4.5 Press the System button on the menu panel to view the system diagram. The loadlock should be empty; if there is a wafer present, Press Vent to vent the loadlock. Remove the wafer when the loadlock sensor reads ATM.

System Window

4.6 Press the Run Recipe button, and select the Pre-Chamber Clean recipe from the drop down list. Press Start to begin processing.

4.7 Once the process is complete, the Chamber Clean recipe needs to be ran. This recipe consists of two ten minute O2 plasma processes, ten minutes with a wafer and ten without. While still in the System window, press the Vent button. Load a blank wafer (glass or Si) in the loading arm, ensuring the wafer flat is oriented correctly.

4.8 Confirm that the process times are set to ten minutes by returning to the Recipes Edit window, and adjust as needed. Note that the second clean recipe is displayed in brackets in the header of the Recipe step list window. Etch recipes that have a cleaning recipe located in brackets indicate that the wafer is removed once the steps have been completed. This will vary between recipes, and is dependent on the type of materials used.

4.9 Once the cleaning recipes have finished, Vent the loadlock and remove the wafer from the loading arm. Load your process wafer into the loading arm, and close the lid.


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Loadlock control

Run Recipe


4.10 Return to the Recipes Edit window, and select the appropriate recipe needed. Edit the process time as needed. Currently there are two standard etch recipes, SiO2 etch, and Pyrex Process.

The Pyrex Process recipe is ideal for wafers with a hard metal mask as the wafer is not unloaded from the chamber during the clean step. Do Not use this recipe for photoresist masks. The recipe consists of 4 steps:

1. Temperature 20o – chuck temperature2. Delay 30s – thermalization time3. Pyrex Process – etch step4. Pyrex O2 Clean – chamber clean with wafer in chamber

Steps 3 and 4 may be repeated as many times as necessary to etch to the desired depth. It is highly recommended that the etch step not exceed 10 minutes due to excessive polymer deposition, and that the O2 clean follow immediately after the etch step.

The SiO2 Process recipe is the standard quartz etch recipe, but will also work for borosilicate etches . This process does unload the wafer for the clean step, and is ideal for photoresist masks. The chuck is cooled to -20C for this process, and does take ~30min to reach this temperature. This recipe will also consist of 4 steps:

1. Temperature -20o – chuck temperature2. Delay 30s – thermalization time3. SiO2 Process – etch step4. Delay 5min – delay time before wafer unload

This recipe cannot be repeated in sequence, and users doing extended etches will need to manually start the process to repeat etches until the desired etch depth is reached.

4.11 Return to the System window once the Recipe has been edited. Start the etch process, ensuring the correct etch recipe is selected. If the recipe uses a lower chuck temperature, there process will not start until the temperature setpoint has been reached. This may result in a delay of up to 30 minutes. Record the run in the logbook. Things to watch out for are the chamber pressure during processing, and the Helium back cooling flow. If there are any warnings or alarms during processing, please contact the designated trainers.

4.12 When the process is complete, the wafer will be in the loadlock. If the wafer fails to unload, the chamber will have to be opened. Again, contact the designated trainers.

4.13 Vent the loadlock. Remove and inspect your wafer. Check for cracks, chips or breaks along the outside edge of the wafer. Ideally there will be no damage, but the likelihood of damage occurring increases with etch time. Small cracks in the wafer may still be able to be etched, but larger cracks or chips will not be able to be etched further.


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4.14 If further processing is required, repeat steps 4.10 to 4.13 until the desired etch is reached. Once processing is complete, return the chuck temperature to +20o.

5. TROUBLESHOOTING

If a wafer fails to unloads or breaks inside the chamber, the chamber will have to be manually opened and cleaned. Contact the trainer or maintenance staff for assistance.

A common error is the He leak up rate (He LUR) out of tolerance error. This usually occurs during the initialization step of a process where the wafer is tested to ensure there is good contact between the wafer and the cooled chuck. The wafer is clamped to the chuck by twelve ceramic fingers, and He is flowed between the wafer and the chuck. If there is a poor seal between the wafer and the chuck, the LUR will exceed tolerance. Users should ensure that wafers are thoroughly cleaned before processing; both front and back-side; and if using a scribe to mark wafers, mark only in the centre of the wafer.

If you encounter an unexpected error or require assistance please contact the primary or secondary trainer listed above. Should they not be available, please contact any staff member for assistance.

6. APPROVAL

QUALIFIED TRAINER: Scott MunroTRAINING COORDINATOR: Stephanie Bozic


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ALCATEL ICP-RIE - University of Alberta nanoFAB · NanoFab 08 October 2010 A Micro Machining &...

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