Glossary of Wafer Map Terms

Wafer Binning Map Die Identification

wafer diameter

wafer flat

wafer notch

bin code

null die

reference die

mirror die

ugly die

edge die

fail die

first die

skip die

map overlay

array dimension



origin location

axis direction

reference coordinates

die size

step size

street size

Lot ID

Substrate ID

Device ID

Product ID


The round wafer used to build chips typically has a diameter of 200 mm or 300 mm. A flat or a small notch is cut into the wafer in order to align it in a repeatable orientation during each step of processing. The wafer map must inform the user of the location of the flat or notch.

Flat Location is either labeled as BOTTOM,LEFT,TOP,RIGHT or in degrees: 0,90,180,270. Unfortunately, when using degrees some map formats do not agree about whether 0 degrees is on the top or bottom.

wafer flat notch orientation


Binning is the process of assigning a bin code to each device on the wafer. Devices may be optically inspected and/or electrically tested. Some are completely rejected. Those that pass may be assigned grades based on the electrical test.

Blue: Null Bin; Cyan: Edge Bin (or Skip); magenta: good/pass; yellow:fail


map overlay - a term used in SEMI E142 for the array of bin codes associated with a substrate/layout. E142 allows multiple maps to be "overlaid" on a single substrate. For example, if more than one test were performed, the results of each test could be recorded in separate maps. However we rarely encounter this and currently don't support it.

array dimension - the X and Y dimensions of the map array. This includes the null die positions. Do not confuse the use of dimension here with a physical length -- it is the size of the array (positive integers only)

rows - the number of horizontal rows in the array.

columns - the number of vertical columns in the array

origin location - one of the 4 possible corners where the array count begins. Labeled either by quadrant (I, II, III, IV) or by name: UpperLeft, LowerLeft, UpperRight, LowerRight

axis direction - the direction in which the array indexes increase for X and for Y. Typically for an origin in the LowerLeft the Axis would be UpRight. However nothing prevents a different axis direction (which often results in negative index values.

reference coordinates - a map file will often state the location (or locations) of reference devices by the array position i.e. REF1: 129,26. It is necessary to know the origin location and axis direction to actually find the reference die. It is also necessary to know whether the index count starts at 0 or 1. (Most maps start at 0 but a few we have seen start at 1. And at least one starts neither at 0 or 1 but sets 0 to the location of a reference die.

Die Size and Stepping

Die Size - the X and Y dimensions of the die that is stepped across the wafer.

Step Size - the distance from the same point on a die to the point on an adjacent die. This is typically larger than the device size - for many wafer map formats this is the number that is of interest.

Street Size - the gap between the edges of adjacent dies. It is there to account for the width of the saw used to singulate the die. This information is typically not useful for equipment that uses the die map. Step Size - Die Size = Street Size.

die size, step size and street size


LotID - wafers are normally fabricated in lots - typically up to 25 wafers per lot. The Lot ID is the number or string assigned to the lot by the fab. It is generally etched into the wafer so it can be read by man and machine.

wafers are processed as a group known as a lot. Each individual wafer has an ID. The lot number and wafer number are etched into the silicon to keep track of things. wafer id scribed

Wafer ID scribed into the margin area of the wafer. You can also see the notch.

Wafer ID - each wafer within a lot is assigned a unique number or string. This is also etched into the wafer.

Device ID - identifies the device that is stepped across the wafer.

Product ID - often used interchangeably with the Device ID.