08-10-2011, 12:27 PM
[quote name='TheChris' timestamp='1312975929' post='10574']
miro, I am not sure but I think you made the wrong assumptions.
The optical encoder I used needed a reflective surface. This was achieved the traditional way by sputtering the wafer with chrome after the lithography process. So this requirement of Imatest can be served.
Concerning the sensor signal, I might misunderstand you. The sensor does not look for 0 and 1, thats the microcontroler input. The sensor measures level of light sensivity, which are transformed into digital outputs by the quadrature encoder via A and B channels. I think this is what you meant when talking about the SinCos encoder function and zero points. But then, what influence does this fact have on what we need? Is it sharpness of the pattern you are concerned about? The lithography mask we used was created without optical processes involved. The optical errors that can lead to low contrast edges on the final pattern on the wafer during lithography, yes. But this is a problem in general and the magnitude of the error is related to the structure size we need.
Klaus suggestion of 20k lines per inch calculates back to ~1.27µm distance from line to line, making it ~0,63µm line width. I have to confess, this is probably out of reach for the capabilities I could provide. But in these dimensions, structure contrast should still not be a problem.
Christian
[/quote]
Well, technically we would only need a "perfect black/white" transition (actually a very dark gray, white). A normal printer can provide an exceedingly sharp edge as long as the test quadrant it is not tilted (which would introduce the typical edge "stepping" issues). We just tilt the print in order to have the suggested 5 degree tilt of the edge which must be measured.
So we don't need something like fine line-pairs. I reckon this is much easier to achieve but I'm clueless regarding the details of the lithography process.
I may be interesting to do some proof-of-concept testing based on suitable scrap material. As mentioned any significant investments are totally out-of-scope anyway. This is a small scale operation here - basically a side job of three enthusiasts rather than a really serious business.
cheers
Klaus
miro, I am not sure but I think you made the wrong assumptions.
The optical encoder I used needed a reflective surface. This was achieved the traditional way by sputtering the wafer with chrome after the lithography process. So this requirement of Imatest can be served.
Concerning the sensor signal, I might misunderstand you. The sensor does not look for 0 and 1, thats the microcontroler input. The sensor measures level of light sensivity, which are transformed into digital outputs by the quadrature encoder via A and B channels. I think this is what you meant when talking about the SinCos encoder function and zero points. But then, what influence does this fact have on what we need? Is it sharpness of the pattern you are concerned about? The lithography mask we used was created without optical processes involved. The optical errors that can lead to low contrast edges on the final pattern on the wafer during lithography, yes. But this is a problem in general and the magnitude of the error is related to the structure size we need.
Klaus suggestion of 20k lines per inch calculates back to ~1.27µm distance from line to line, making it ~0,63µm line width. I have to confess, this is probably out of reach for the capabilities I could provide. But in these dimensions, structure contrast should still not be a problem.
Christian
[/quote]
Well, technically we would only need a "perfect black/white" transition (actually a very dark gray, white). A normal printer can provide an exceedingly sharp edge as long as the test quadrant it is not tilted (which would introduce the typical edge "stepping" issues). We just tilt the print in order to have the suggested 5 degree tilt of the edge which must be measured.
So we don't need something like fine line-pairs. I reckon this is much easier to achieve but I'm clueless regarding the details of the lithography process.
I may be interesting to do some proof-of-concept testing based on suitable scrap material. As mentioned any significant investments are totally out-of-scope anyway. This is a small scale operation here - basically a side job of three enthusiasts rather than a really serious business.
cheers
Klaus