In this lesson

One wafer can mislead you: a pattern may be chance. A lot can show what repeats. This lesson shows how to look across all the wafers at once, and how to label wafers so you can compare them.

• Combine every wafer of a lot into one stacked map
• Select the same dies on every wafer
• Name wafer splits and show them on the maps
• Name bins and choose which ones count as a pass

One card per wafer

A gallery shows each wafer on its own card. This is EDGE-LOT-01, eight wafers with an edge-ring defect. The buttons above act on all the cards at once (lesson 02).

Stacked Hard Bins

Stacked Hard Bins draws one card per bin. Each die position is coloured by how many wafers had that bin there: 0 to 8 here. Pass is high everywhere except a ring at the edge, where the defect sits. A defect that repeats on every wafer is far easier to see here than on any single map.

Stacked Soft Bins

Stacked Soft Bins does the same for soft bins, so each lot-level failure mode shows as its own map.

Stacked Test Values

Stacked Test Values draws one card per measured test (three here), with the values combined across the wafers. The header says how many wafers were stacked and how they were combined, so you always know what you are looking at.

Wafers that are not stacked

Wafers with other pass bins or ring counts are not stacked, because their results would not be comparable.

Select dies on one wafer

Selecting dies is how you ask "what is going on here?" about part of a wafer. Drag a box on a map: the dies inside it are selected and the rest fade. Ctrl or Cmd + click adds or removes a die; a click outside the wafer clears it. Lesson 08 charts a selection.

Select the same dies on every wafer

By default each card selects on its own. Turn this on when you want to check whether a region behaves the same way on every wafer.

One box, every wafer

Drag a box on one wafer and the same positions are selected on every wafer. The badge counts them, and the button clears them.

(Charts of the selected dies are covered in lesson 08.)

Pick whole wafers

To look at some wafers rather than some dies, Ctrl or Cmd + click a card's header to pick that wafer. The toolbar counts the picked wafers. Right-click a picked card and the charts and tables cover every die of every picked wafer.

Splits in the labels

With Show split in wafer map labels ticked, the split follows the wafer ID on every card.

Plain wafer IDs

Untick Show split in wafer map labels and the cards show plain wafer IDs. The assignments are unchanged either way. The option only changes what the labels say.

Remembered for the lot

You do not have to assign splits again. Reopen the same lot and its splits come back, with the dialog open to show them. Clear all forgets them. A file with no lot ID cannot be matched, so save its splits to a CSV.

Bin definitions…

Bin numbers mean little until they have names, and which bins count as a pass decides the yield of every wafer. Setup ▾ → Bin definitions… opens a table of every hard and soft bin, with its die count, a name, whether a hard bin passes, and optionally the colour it is drawn in on the maps.

STDF and ATDF files carry names and pass flags of their own, so the table starts filled in. Edit a name or a colour in its cell. Nothing changes in the lot until you press Apply.

Recap

• Stacked modes turn a lot into one map per bin or test, so what repeats stands out
• Select the same dies reads one region across every wafer
• Splits name wafers the file doesn't, and show on every label
• Bin definitions… names bins, colours them and chooses which hard bins pass, with the yield shown before you confirm

The next lesson moves from maps to charts, and compares groups of wafers such as these splits.

More in the wafer map guide