ZReference: compensated contact?

[m-far]

I'm trying to retrieve the value of the contact position after compensation (i.e. with on the fly active), but I have yet to find how to do this.

If I use the move_chuck_contact command, I go to the compensated position; but if I query the contact position using the command 'get_chuck_site_height', I get the uncompensated contact position. Furthermore, I'm also not seeing a way to retrieve the compensation offset.

Is there a command I'm not finding to do this? if not, would it be possible to add a way to get this information?

[beltoforion]

XY compensation is a measured function of x and y across the full chuck area. As far as I know, there’s no direct way to read out the full compensation surface.

To move forward, we’d like to understand your use case a bit better. What’s the reason you need this value?

[m-far]

There's 2 situations in which we would find the information useful:

1. We are working with the SiPH system, developing our routines to do fiber to wafer alignment. For flexibility, we have separate routines for wafer and fiber movement, that are then called from a main script to do the full test. I would like to include in the fiber routines a check if the wafer is in contact before doing any alignment or contacting the FAU; as for example if the wafer is not in contact, I could end up in a situation where I lower the fiber too much and then in another section of the test I put the wafer in contact resulting in a fiber crash. It's mainly a safety check, which is easy to do if I'm working on the PC with sentio where there are various indicators of the status of the wafer contact; I would like to have that also from remote.

2. We had a situation in the past where the Z-compensation kept on increasing as we stepped across the testing sites. We managed to make it work, but it would be very useful for us to keep track of the compensation values, so we can quickly catch if this happens again.

I hope this clarifies a bit the use cases. Let me know if there is any additional information that could be useful.

While I'm here, another command that would be useful to have is a way to read the vacuum level on the machine, as this is also something we had issues with in the past that we would like to track (maybe this needs it's own issue).

[beltoforion]

Thank you for the clarification.

Regarding 1.)
There is a remote command to query wether a stage is in contact or not: status:get_prop z_position_hint,chuck. This is a so called module property. This is a lesser known feature explained on Page 12 of the remote command documentation (at least in my version). It should tell you wether the wafer is currently in contact or not. This command would only be usefull if you are already at contact height.

If your problem requires knowing wether a given z height will be at or below contact height without already being there. That is not possible at the moment. All workarounds i can think of would require you to actually go into contact and then computing the difference between the actual absolut z position and the defined contact height.

In Principle we do have the information in SENTIO and we could extend the function of "status:get_prop z_position_hint,chuck" to take a z-height as an optional parameter. Based on that z-height the system could then report to you what this position would actually be if you would move there.

Do you think that using status:get_prop z_position_hint,chuck as is will already solve your problem?

Regarding 2.)
I'm not sure is we can actually read the vaccum meter directly from SENTIO yet. This information may only be available in the machine layer and may be not even there since the meter may not be controlled. The vacuum meter may merely be signalling vacuum is there or not. I need to check this with the rest of the development team in Taiwan.

We do have the command get_chuck_site_status which should report back wether vasuum is on or not. But it will not report beck the target levels.

[m-far]

Thank you for the fast response.
regarding 1) the command you suggested is exactly what I needed, thank you; I missed it in the manual.
It would be nice to have a command to track the PTPA offsets (i.e. compensated positions), but indeed as suggested it is possible to go in contact and measure the chuck real position and compare it to the 'uncompensated' contact position.

regarding 2) I was thinking, we don't necessarily need to get the vacuum level via sentio itself, assuming there is a way to communicate directly with the vacuum sensor, not sure if this is somehow easier.

[Hoca-Chen]

Hi

Thanks for your feedback.
Regarding 2:
Unfortunately, the vacuum meter is not able to read out the value so far.

Can you share the agent of prober that we can feedback these situations?
or also can contact the agent for this information.
It could be a better solution for this case.