What is the overglass and glass in layout?

[ee484]

Hi,
Q1) what does a glass mean in layout? Does this mean an opening that serves connection between a top metal and bondwire?

Q2) What is overglass?

Q3) Why is it called glass? Any insulator can be called glass?

Q4) I also know that the insulator on the chip is called passivation. What is the relationship between passivation and overglass?

Q5) Are "pad layer" and "overglass layer" the same?

any reference and good explantions are welcome!! (with figures)

for your reference, i.e., **broken link removed**

 

[cmos_dude]

opening in passivation layer

Q1) what does a glass mean in layout? Does this mean an opening that serves connection between a top metal and bondwire?
A: Yes, the glass layer defines the opening to the external world for bondwire.
The glass layer is a negative mask and defines an opening in the passivation layer.

Q2) What is overglass?
A: The same as glass or the passivation layer (whichever way you might like to call it)

Q3) Why is it called glass? Any insulator can be called glass?
A: The pad is not covered by the protective passivation layer (a glass material that protects the die) and thus is an area that is vulnerable to dirt and other foreign objects. Hence it is called because of the material of passivation.

Q4) I also know that the insulator on the chip is called passivation. What is the relationship between passivation and overglass?
A: It is the same thing. But note that the passivation layer is a negative layer

Q5) Are "pad layer" and "overglass layer" the same?
Sorry but I have not heard the term Pad layer before...Maybe yu can through some more light on this aspect.

--cmos_dude

 

[ee484]

overglass

Thank you cmos_dude,

Let me ask a couple more questions,

1) Is negative mask (or layer) important? Why did you mention it?

2) In LSW, at least the processing I am using, has the layer called PAD. It does not have glass, overglass, or passivation layer.

(I thought passivation layer is the insulator that covers the top metal. So that I did not think passivation layer open the opening for the bonding pad. But, maybe I was wrong.)

Thanks, cmos_dude

 

[cmos_dude]

Re: overglass

Hi ee484

1) Is negative mask (or layer) important? Why did you mention it?
A: Its not important from a layout designer's perspective. I just mentioned it to make the process more clear to you such that the glass layer defines an opening and not insulation.

2) In LSW, at least the processing I am using, has the layer called PAD. It does not have glass, overglass, or passivation layer.
A: The name that you see in your LSW is not important. What matters is the GDS number related to that layer and what it resembles in the design rule deck provided by the foundry. Try to trace back the layer to the rule deck and get more clarification.

--cmos_dude