Creating and Displaying Incoming Wafer Fiducials

Wafers that are to be processed for flip chip arrive at the package foundry with a number of fiducials in the corners (and possibly the top/bottom) and if one wishes to produce a package document that shows the locations these have to be drawn separately as that information is not part of a shot map or wafer map.

GDS-SR now supports importing the fiducial's location, size, shape and color. The imported data is shown on the display and on any high resolution bitmap that is exported. However it does not show up in any output GDSII file generated as part of the mask generation process.

Fiducials in upper left and lower right. They are too small to see at this resolution.

Syntax for Defining Wafer Fiducials

This can be either incorporated into a configuration/script file that is used to generate the entire stepped mask or it can be created stand-alone and then selected by the user to generate a display of the wafer fiducials. Arguments are space delimited.

[INCOMING_FIDUCIALS]                                   <-- required section head
; Name     Shape  Size   Cen-X  Cen-Y  RGB Color       <-- comments allowed - must have ; as first character 
POLYMER_UL ROUND  1000  -67000  70000  225 120 163     <-- first argument is a user defined name; no spaces  
METAL_UL   ROUND  1000  -67000  67000  120 155 100     <-- second argument is shape: ROUND or SQUARE
REF_UL     ROUND  1000  -70000  67000  120 120 200     <-- third argument is size (in same units as wafer)
POLYMER_LR ROUND  1000   67000 -70000  225 120 163     <-- 4th/5th arguments are center coordinate
METAL_LR   ROUND  1000   67000 -67000  120 155 100     <-- 6th/7th/8th arguments are RGB color triad (0-255)

User Interface

When placed into a GDS-SR script used to generate a mask no user intervention is needed. However if you are running GDS-SR from the GUI you can append or replace incoming fiducials from the Wafer pull down.

To insert fiducials choose either Append Fiducials ... or Replace Fiducials ... from the Wafer drop down. Append will add the newly selected fiducials to any existing ones; Replace will clear any existing fiducials with the new ones.

Knocking Out or Deleting Packages

It is standard practice to delete any RDL packages that would cover the incoming wafer fiducials. This can be done either through the GDS-SR script or manually from the GUI. If done manually, it does not matter whether the die are deleted before or after importing the incoming wafer fiducials.

Hi Resolution Bitmap

At standard screen resolutions it may be difficult or impossible to "see" the incoming fiducials because they are so small relative to the size of the wafer. A typical fiducial may be 500 um while the wafer is 200,000 to 300,000 um in diameter.

Since the purpose of generating these fiducials are for documentation then we recommend that the user:

1. increase the size of the incoming wafer fiducial from its true size.
2. output a high resolution bitmap

In the image below, the incoming fiducial diameters were increased from the nominal 500 um to 1000 um and the output bitmap was set to 4000 pixels wide instead of the 1200 pixels wide that would have been generated from the screen resolution. The image below is a 680 pixel wide crop of the overall image.