Wafer maps are used in the back end of the IC manufacturing industry to annotate the die on a wafer - the annotation either indicates the die's identity or whether the die is good or bad.
Our particular interest in wafer maps is their use as an aid to create the layout for bump redistribution circuitry that is added to the wafer after the regular manufacturing is completed. However many test engineers have found this program useful to move data from a format they cannot use into one that drive software or equipment.
SINF formatted wafer map
Many Different Formats and Syntax
While the basic data of a wafer map is fairly simple, foundries that provide mask data do not adhere to a single standardized format. This means that any software utility designed to convert such files must support a number of different formats.
Step Size Missing?
Further, we have discovered that some of the wafer maps lack essential data needed to create a physical layout -- for example, some maps are missing the step size of the die. This essential information must be manually entered in order to actually produce a layout. Fortunately the step size is fairly easy to obtain and enter manually.
Positional Data Missing
Finally, the wafer maps appear to generally be missing a critical parameter from the mask designers point-of-view: The absolute position on the wafer of the array of devices. This is the most serious issue facing a mask designer who is attempting to use the wafer map as a way of generating his redistribution mask.
Standard Formats for Wafer Maps
There are standard formats for wafer maps available from the SEMI organization: an older one still in wide usage is called SINF. We've documented the ASCII version of SINF here. A newer version called SEMI 142E is XML based on much more powerful as it supports wafers, strips, double sided packages and so on. We're only concerned with SEMI E142 for single sided wafers. See a SEMI E142 example here ...
The WMapConverter Utility
WMapConverter reads a number of different map file formats and produces any (or all) of the following outputs:
Standard SINF ASCII Wafer Map
WMapConverter main dialog
WMapConverter Die Dialog shows count and allows ID remapping
How it WMapConverter Works
The user loads the wafer map file and uses the pulldown to indicate what "flavor" of wafer map is to be converted. (See supported map formats ...) Once loaded the user presses the Scan ... button.
After the input file is scanned, WMapConverter displays the critical input parameters in this section. If a particular flavor of map file is missing one or more parameters, the user needs to enter those values. This might be the stepping information, the units or the position of the wafer notch. Row and Column data can always be determined by the program for a valid wafer map file.
The user selects the directory for the output file along with the "base" name. The output name will use the base name plus an extension: txt for sinf files, gds for GDSII stream and dxf for DXF file.
The user can also select the units of the output file.
Rotation - The data can be rotated clockwise about the center in increments of 90 degrees. This is useful when the foundry provides the data with the notch in one position (say on the left side) but the RDL designer works with the notch in another position (say on the bottom.)
Move - since the wafer map has no positional information the entire array is intially centered about 0,0. However it is rarely the case that the array is actually centered 0,0 on the wafer. Therefore the program allows the user to add a shift to position the array exactly where it should be on the wafer.
Unfortunately, determining the correct value of shift is not always easy given the nature of the data provided by the wafer foundry. We'll discuss ways of determining that.
Die ID Remapping
The SINF map file format has strict requirements for the ID values of each die. Other map formats don't follow these restrictions so it becomes necessary to remap those into legal SINF values. The layer dialog not only provides the user a quantity for each Die ID, it allows the user to change the ID in the converted output.For example:
Input Map --> SINF Map * --> __ X --> 01
Special Graphical Elements
The actual size of the wafer is not part of the wafer map specification. The user can enter the wafer diameter and margin and also have cross hairs drawn in the GDS and DXF Output. These additional items make it much easier to make measurements in the layout.
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