Semiconductor Back-End Processing Steps

[Semicon Enthusiast]

Dear Peers,

I am currently investigating the semiconductor back-end processing market a bit more in detail. But first things first, let me quickly define "back-end" since different people have different understandings about it. When I talk about semiconductor back-end processing I mean the first process step AFTER the wafer is finished getting its final structure.

For me, the first step of the semiconductor back-end processing starts with the TAPING. So from now on I would need your help. I want to understand the full process chain and therefore I kindly ask you to check my following understanding of the processing process chain and add any comments if I forgot something:

1) Taping
Reason:
- Applying back-grinding tape in order to protect the precious and finished front-side from any damage that could occur during the upcoming dicing process

Things to consider:
- What backgrinding tape to use?

- Tape thickness​

- Tape adhesive level/power​

- Tape material (PVC/PO)​

- Taping parameters

- Standard taping or vacuum taping​

- Roller speed​

- Applying force​

- UPH requirement

- Semi-auto or fully auto equipment​

​

2) Grinding
Reason:
- Thinning down the thickness of the wafer to the desired final thickness of the chip

Things to consider:
- TAIKO or non-TAIKO
- Polishing or only grinding

- Tape thickness​

- Tape adhesive level/power​

- Tape material (PVC/PO)​

- Grinding parameters

- Spindle feed speed​

- Wheel choice (Bond material, diamond size)​

- Surface roughness​

- UPH requirement

- Semi-auto or fully auto equipment​

​

​

3) Peeling
Reason:
- Removing the backgrinding tape after the grinding process (might be an inline process)

Things to consider:
- Residue free peeling
- Peeling table to be used (TAIKO (non-contact) or non-TAIKO (standard))
- Peeling parameters

- Removal speed (might be different on different areas of the wafer)​

- UPH requirement

- Semi-auto or fully auto equipment​

​

4) Probing
Reason:
- Checking the functionality of the chip(s) after the stressful processing of grinding

Things to consider:
- Test all / only a few dies
- Testing on tape and frame (in this case different process chain)
- Probing parameters

- Probing speed​

- UPH requirement

- Semi-auto or fully auto equipment​

5) Mounting
Reason:
- Putting the wafer on dicing tape and dicing frame in order to prepare it for the upcoming dicing (singulation) process

Things to consider:
- Which wafer type

TAIKO (Vacuum mounting) or non-TAIKO (standard mounting)​

- Which dicing tape?

- UV tape or standard tape​

- Tape thickness​

- Tape adhesive power​

- Frame type?

- Metal or Plastic​

- Mounting parameters

- i.a. Vacuum level​

- Mounting speed​

- UPH requirement

- Semi-auto or fully auto equipment​

​

6) Dicing

Reason:
- Singulating the dies from the wafer

Things to consider:
- Technology?

- Blade dicing​

- Laser dicing (SD or "laser" dicing)​

- Plasma dicing​

- Dicing parameters

- Spindle feed speed​

- Blade RPM​

- Blade type (Bond material, diamond size)​

- Laser parameters​

- UPH requirement

- Semi-auto or fully auto equipment​

​

7) UV irradiation (only necessary in case of UV tape) - might aswell be inline in dicer

Reason:
- Reduce adhesive power to almost 0 to pick up the dies

Things to consider:
- UV intensity needed
- UPH requirement

- Semi-auto or fully auto equipment​

​

So far so good. I want to make this a very detailed list with all factors to be considered withing the single process steps. So please feel free to add ALL your comments and inputs in the different process steps. I will try to update this list all the time in order to have a great overview about all the things that need to be considered when we are talking about the mentioned 6 process steps.

Thank you very much.

Tobias

 

[Semicon Enthusiast]

Dear Peers,

another question that popped up from my side:

What kind of differentiations are done in fabs? Depending on the application the chip goes in there are some process steps that are present at some but not present at other (e.g. backside metal for IGBT but not for MEMS or sensors. Could you help me complete this list?

Power
MEMS
Sensors
CMOS

I know that this differentation could be done up to a lot but I am especially interested in the differentiation in regards to the back-end processing of those wafers. Power for example could be either IGBT or MOSFETS but since the back-end processing for both it is the same, it makes no sense to "split" them into two different categories.

I hope it is quite understandable what I am asking you guys.

Thanks,
Tobias