Substrate mapping (or wafer mapping) is a process in which the performance of
semiconductor devices
A semiconductor device is an electronic component that relies on the electronic properties of a semiconductor material (primarily silicon, germanium, and gallium arsenide, as well as organic semiconductors) for its function. Its conductivity li ...
on a substrate is represented by a map showing the performance as a colour-coded grid. The map is a convenient representation of the variation in performance across the substrate, since the distribution of those variations may be a clue as to their cause.
The concept also includes the package of data generated by modern
wafer testing Wafer testing is a step performed during semiconductor device fabrication after BEOL process is finished. During this step, performed before a wafer is sent to die preparation, all individual integrated circuits that are present on the wafer are tes ...
equipment which can be transmitted to equipment used for subsequent 'back-end' manufacturing operations.
History
The initial process supported by substrate maps was inkless binning.
Each tested die is assigned a bin value, depending on the result of the test. For example, a pass die is assigned a bin value of 1 for a good bin, bin 10 for an open circuit, and bin 11 for a short circuit. In the very early days of wafer test, the dies were put in different bins or buckets, depending on the test results.
Physical binning may no longer be used, but the analogy is still good. The next step in the process was to mark the failing dies with ink, so that during assembly only uninked dies were used for
die attachment
In electronics manufacturing, integrated circuit packaging is the final stage of semiconductor device fabrication, in which the block of semiconductor material is encapsulated in a supporting case that prevents physical damage and corrosion. ...
and final assembly. The inking step may be skipped if the assembly equipment is able to access the information in the maps generated by the test equipment.
A wafer map is where the substrate map applies to an entire
wafer
A wafer is a crisp, often sweet, very thin, flat, light and dry biscuit, often used to decorate ice cream, and also used as a garnish on some sweet dishes. Wafers can also be made into cookies with cream flavoring sandwiched between them. They ...
, while a substrate map is mapping in other areas of the semiconductors process including frames, trays and strips.
E142
As with many items in the Semiconductor process area, also for this process step there are standards available. The latest and most potential standard is the E142 standard, provided by th
SEMI organization This standard has been approved via ballots for release in 2005.
It supports many possible substrate maps, including the ones named above. While the old standards could only support standard bin maps, representing bin information, this standard also support transfermaps, which can help in tracing back dies on strips to the locations they come from off the wafer for example.
External links
SEMI organization organization which is working on semiconductor process standards.
Semiconductor device fabrication