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Chip making process
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brucehoult:

--- Quote from: Kjelt on October 16, 2018, 09:15:56 am ---
--- Quote from: ZeroResistance on October 16, 2018, 05:11:33 am ---So what is the terminology is a reticle = a mask? 
--- End quote ---
Yes it is.

--- End quote ---

I believe in FAB usage mask and reticule are actually alternatives.

A mask is the same size as the silicon wafer and the entire wafer is exposed in one operation. A reticule is effectively a small (e.g. 25mm x 25mm) but very precise mask and each part of the wafer is exposed in turn, using a very accurate stepper mechanism.
ZeroResistance:

--- Quote from: brucehoult on October 16, 2018, 09:44:52 am ---
--- Quote from: Kjelt on October 16, 2018, 09:15:56 am ---
--- Quote from: ZeroResistance on October 16, 2018, 05:11:33 am ---So what is the terminology is a reticle = a mask? 
--- End quote ---
Yes it is.

--- End quote ---

I believe in FAB usage mask and reticule are actually alternatives.

A mask is the same size as the silicon wafer and the entire wafer is exposed in one operation. A reticule is effectively a small (e.g. 25mm x 25mm) but very precise mask and each part of the wafer is exposed in turn, using a very accurate stepper mechanism.

--- End quote ---
So lets say I send my design to the mask maker and he sends me back a 1mm2 size mask or reticule and for each of the layers.
Or does the mask maker make a grid of the whole design based on what the foundry silicon wafer size is, and and then gives me that for all the layers And then this is submitted to the foundry right? and then they expose the whole wafer at one go and you get he desired number of chips from that wafer.
This would be the process wouldn't it?
In what case would the foundry want to selectively expose a reticule? Because that seems to be a very slow process?
Kjelt:

--- Quote from: brucehoult on October 16, 2018, 09:44:52 am ---I believe in FAB usage mask and reticule are actually alternatives.
A mask is the same size as the silicon wafer and the entire wafer is exposed in one operation. A reticule is effectively a small (e.g. 25mm x 25mm) but very precise mask and each part of the wafer is exposed in turn, using a very accurate stepper mechanism. 
--- End quote ---
I never heard of that. Perhaps in the far past it was done that way with 2" wafers or so but modern stepper scanners contain a reticle holding a single processstep of a single or more dies(chips). This depends on the size of the die. And the wafer is exposed in steps (stepper) or in a scan (scanner) where the reticule and the wafer move in opposite directions (see wiki below).
The whole wafer is so exposed in a couple of scans which totally takes less than 10 seconds.
These machines nowadays do 250 wafers/hour.
https://en.wikipedia.org/wiki/Stepper

BTW the reason is simple you can not focus an entire wafer upto the required nm resolution, your lens would be 1meter diameter and more expensive than the entire fab. The reticule is 4x bigger than the final die so if any dust particle is on the reticle it will not influence the final product.
Richard Crowley:
I remember in the late 1970s, 4-inch (100mm) wafers were still being exposed with whole-die wafer methods using equipment from Perkin-Elmer.  Their optical division developed the Keyhole-9 satellite spy cameras and were later responsible for the Hubble optical system.  When feature sizes started getting smaller, it was getting difficult to expose a whole wafer because minute vibration would blur the image. I remember at one time personnel were deployed as train-spotters to warn of approaching rail traffic so that they could suspend imaging while the train passed.  Giant timbers were wedged between the ground-floor slab and the floor of the fab to reduce the vibration.

As @Kjelt mentioned, current practice is to use 4x reticles to step and repeat exposure across 300mm wafers.  Laser interferometery is used to ensure accurate positioning for each exposure.  And it is good enough that it has operated perfectly during an earthquake. A far cry from the days of wedged timbers and trainspotting.

ED: "whole-wafer", not "whole-die"!
coppice:

--- Quote from: Richard Crowley on October 16, 2018, 11:42:16 am ---I remember in the late 1970s, 4-inch (100mm) wafers were still being exposed with whole-die methods using equipment from Perkin-Elmer.  Their optical division developed the Keyhole-9 satellite spy cameras and were later responsible for the Hubble optical system.  When feature sizes started getting smaller, it was getting difficult to expose a whole wafer because minute vibration would blur the image. I remember at one time personnel were deployed as train-spotters to warn of approaching rail traffic so that they could suspend imaging while the train passed.  Giant timbers were wedged between the ground-floor slab and the floor of the fab to reduce the vibration.

As @Kjelt mentioned, current practice is to use 4x reticles to step and repeat exposure across 300mm wafers.  Laser interferometery is used to ensure accurate positioning for each exposure.  And it is good enough that it has operated perfectly during an earthquake. A far cry from the days of wedged timbers and trainspotting.

--- End quote ---
The exposure is about the same size now. The active area of the reticule is of the order of 100mm x 100mm.
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