Sawatec SM-150 for ebeam resists ‒ Center of MicroNanoTechnology CMi ‐ EPFL

Used liquids and/or solvents can be dangerous for the skin. Always wear protective gloves during operation!

Operate carefully following the instructions on the manual available on the coater bench to avoid serious damage to the tool (especially when mounting or unmounting chucks).

Introduction

The Sawatec SM-150 spin coater is a manual coater for small samples and wafers up to 150 mm. The coater is located in the processing room of the ebeam zone (zone 7), and is dedicated to ebeam lithography ONLY !

Following resists are currently authorized to be coated here: MMA, PMMA, ZEP, CSAR, HSQ, FOX16, Electra92, nLOF.

Please do not bring in any other material and do not try to coat any other resist or substance.

If you have any special request, please, ask ebeam staff before.

To use the coater, you must were additional protective gloves. Almost all resists are spun from a solution containing some type of organic solvent (e.g. Anisol, MiBK). Gloves are also needed for the use of the solvents bench when cleaning the spincoater chucks.

Available chucks

5 chuck sizes available: 6″, 4″, 2″, 1″ wafer and for smaller chips

Chucks are available for 150mm wafer, 100mm wafer, 2″ wafer, 1″ wafer and small chips. Please, always select a correct size chuck – make sure that your chip/wafer covers the entire elevated platform of the chuck. Attempting to coat smaller chip/wafer on a larger chuck will result in the resist being sucked into the central vacuum tube, and also in partial coating of the chuck platform surface, which will lead to resist being sucked in on the next coating attempt. If enough resist builds up on the top surface of the chuck, the vacuum may get weaker and the spin coater might not allow the coating sequence.

Select and clean chuck

The chip chuck should not be cleaned with acetone as it has an o’ring on the top: acetone will damage the o’ring.

After selecting a proper size chuck, please, clean it with acetone (except for the chip chuck) on the solvents bench. Acetone wash needs to be followed by IPA rinse before drying with Nitrogen gun.

Prepare your sample and resist – ready to coat

In order to optimize your time on the tool, it is highly recommended that you come with your wafer ready to be coated (hot plate drying, O₂ descum etc.).

After selecting the resist available in the cabinet or in the fridge in the resist storage area, it is necessary to weigh the bottle using the precision balance located to the left of the PC in the ebeam preparation area.

To ensure sufficient resist stock, it is essential to enter the quantity of resist used in the dedicated spreadsheet for every use, even for very small quantities.

Now you are ready to coat your sample and follow the instructions for using the spin coater.

Operating the Sawatec SM-150 Spin Module

Do not place/replace chuck in automatic mode, only in Standby mode (cf. below).

1. Login

It then turns orange when you succeed in the login.

2. Exit alarm status

After login, the system will be in “alarm” status.

Click on the warning button on the interface (no matter the window on the interface, you will see this red icon):

You will enter the “Alarm window” (cf. below). Then press the green check button to acknowledge the alarm, click as many times as needed to clear all the alarms.

Each alarm must be acknowledged, before the machine can continue.

Alarm window fully cleared

Exit this window by clicking on the Exit door (right bottom corner).

N.B. Every time you log on the tool, you will need to clear warnings.

3. Equipping and exchanging the spin chuck

Before any action to insert/replace the chuck, you need to switch to “Standby” mode.

Before automatic can be started, mount an appropriate chuck onto the chuck holder and apply the substrate. To do so, proceed as follows:

Switch to Standby mode: click on the following button to enter the Standby mode.

Now, you can safely load your chuck following these steps:

You are now ready to load your sample.

4. Loading your sample

Go to Automatic mode by clicking on the following button:

Recipe selection is done by pressing on the name of the recipe box followed by a click on the green check button to acknowledge your choice.

1 – Click on the box name to access recipe scrolling menu, 2 – Scroll and select the recipe, 3 – Confirm your choice

Load your wafer/chip on the chuck. To help yourself centering a wafer you can use the special twizzer (located in the chuck basket).

Activate the vacuum to check the vacuum efficiency – press the VAC button (right bottom corner on the tool).

The pressure should be between [-1.0, -0.4] Bar. Above -0.4 Bar the system will not accept to spin and will show corresponding alarm: “25 Vacuum time out”.

Use a pipette to dispense the resist from the bottle onto the wafer. For 4” wafers, 2ml is dispensed at the center. For small chips, cover the complete surface with resist and empty the excess resist directly into the aluminum boil receptacle.

When done, dispose of the pipette in the dedicated trash and close the lid.

5. Start the coating

Start the spin-coating sequence by pressing the START button next to the VAC button (right bottom corner).

Wait for process completion (remaining time on the interface screen). You will hear 3 beeps followed by the vacuum pump shutdown sound.

Before taking out your sample, open the lid, then on the interface click on Standby mode button to secure the spinning motor:

You can transfer out your sample and logout from the tool.

6. Clean and store

After transferring out your sample, you need to unmount the chuck and clean it with Acetone/IPA/N₂ air gun (except for the small piece chuck that should NOT be cleaned using acetone). Put it back in the chuck basket.

If you have any questions or problems, please contact the CMi staff (Makhlad or Zdenek).