Photolithography :: Photoresist

See the wafer spinning. Now it's going to dump the resist onto the there. See, there you go.Now it's spreading it.

You know when you spread this resist out, it rolls underneath the back of it  and goes along there and stick everywhere. So something came underneath it and washed it out.

 Oh really. Ya.

So you have it built in? You can just about see it on the edges dripping. But, that's finished now.  Now the bottom so been washed out so they don't stick on the belts.

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Photolithography :: Applying the Mask

The wafers have been coated with the resist and they are about to go to the mask printing.

Mask printing, so all of these wafers are getting printed in the same way. 

That's right they are now getting printed and this is called a wafer steper. It's printing the mask actually onto the resist.

So this prints the mask onto the wafer which then goes to the developer.

That's right. You have a resist coated wafer coming up here. So we can see the wafer was coated with the resist and now the mask is actually being transferred to the resist using ultraviolet light.

So I see it's just put on back and it's taking the next one.

That's right. It's onto the next one and it stamps each device.

It goes pretty fast.

It's not too bad. I mean at the moment it's centralizing the wafer and finding it's coating and now it's about to expose the backing.

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Photolithography :: Developer

The developer gets poured on. The wafer is now sitting being developed. It's developing.

It's going to spray for 10 seconds. It's rinsing.

So first it got developer put on and now it's getting rinsed.

Developer is put on, it develops, rinsed, and then it's spun. And that's the end and now it will come up.</center>

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Photolithography :: Inspection

Now you have to answer a silly question.

What's that? Why is the room yellow?

The room is yellow so that, because resist gets exposed to white light it will be...

It goes bad.

Yeah, it's photosensitive. It does not respond to white, mean yellow light.</center>

How long does it take to do an inspection?
Just a couple of minutes per a wafer.</center>

And you're looking for what in particular? Any defect or unexposed resist. And for correct alignment to the previous layer.