Wafer Map — User Guide¶

This guide describes the display and analysis features of the wafer map viewer. It is written for users who may be semiconductor test engineers, device engineers, and yield engineers or anyone else who may use a wafer map application — not for developers integrating the wafermap library.

Some features depend on what data the application has loaded (bin names, test definitions, spec limits, reticle geometry). Where this applies it is noted.

Getting oriented. The wafer map is an interactive viewer. A toolbar is always present at the top-right of the map — use it to change what the colours represent, toggle overlays, rotate or flip the wafer, zoom, select dies, and open the summary panel. Hover any die for a tooltip; the panels and tooltips always report the original die grid coordinates, never the on-screen position after a rotate or flip.

1. Reading the map¶

1.1 Die grid and coordinates¶

Each square on the wafer represents one die. The position labels you see — in tooltips, axis ticks, and selection readouts — are die grid coordinates: usually the X and Y step indices from the prober (integers such as −7, 0, 5). They are not millimetre values.

These coordinates are always the original grid values. Rotating or flipping the display does not change the coordinate labels — a die at (3, −2) always reads (3, −2) regardless of how the wafer is oriented on screen.

1.2 Wafer orientation¶

The notch (shown as a V-notch or flat edge) marks the physical reference edge of the wafer as configured. Use the Orientation toolbar controls to rotate or flip the display to match your convention; die coordinates are unaffected.

An example wafer bin map above and below the same wafer rotated 90°. The notch has moved, but die coordinates — shown in tooltips — remain their original grid/prober values.

1.3 Die appearance¶

No-data grey and partial-die grey are visually distinct. A no-data die is not a fail; it simply has no result recorded. Edge-excluded dies are shown dimmed and are not counted in yield calculations.

1.4 Legend and colorbar¶

Bin modes show a discrete colour legend: one swatch per bin, with bin number and name if the application has supplied bin names.

Value mode shows a continuous colorbar: the colour scale runs from the minimum to maximum value, with units when available. The colorbar is informational only — clicking it has no effect. To filter by spec status, use the Colour by spec option in the Overlays menu (available when spec limits are defined for the active test).

Clicking a bin swatch in the legend filters the display to that bin (see Highlight bin).

2. Plot modes¶

The active plot mode determines what the colour of each die represents. Use the Plot mode toolbar dropdown to switch. Available modes depend on what data the application has loaded.

Stacked modes are only available on lot-stack maps (multiple wafers combined into one display). The panel identifies how many wafers were stacked and which aggregation method is active.

Test Value mode — colorbar range and spec limits¶

When spec limits are defined for the active test, two additional display options become available:

• Colorbar range — Data / Spec: switches the colorbar scale between the actual data extent and the spec limit bounds. Changing this affects only the colour scale; it does not change which dies are flagged as out of spec.
• Colour by spec: when active, dies within spec are shown in a pass colour and dies outside spec are highlighted — blue for below the Lower Spec Limit (LSL), red for above the Upper Spec Limit (USL). Both flags apply independently; a die can be flagged on either or both limits.

3. Toolbar controls¶

The toolbar sits at the top-right of the map and is always visible. Controls that are not applicable to the current mode are hidden automatically. (Hovering the map shows die tooltips — a separate thing from the toolbar, which is always present.)

Single map¶

	Control	Description
	Plot mode	Switches the active plot mode (see Section 2). When multiple tests are available, a test selector appears alongside it.
	Aggregation method	Stacked modes only. Selects how values from multiple wafers are combined per die position: Mean, Median, Std Dev, Min, Max, or Count.
	Overlays	Check-menu of optional display layers: XY axis indicator, ring boundaries, quadrant lines, die coordinate labels, reticle grid (when geometry is configured), and spec pass/fail highlighting (Test Value mode with limits).
	Colour scheme	Switches the colour palette used for value and stacked modes. Available schemes depend on what the application has registered.
	Log scale	Test Value and Stacked Test Values modes only. Applies a log₁₀ scale to the colour mapping. Only active when all displayed values are positive.
	Legend style	Bin modes only. Controls where the bin legend is positioned relative to the map: Default (right), Compact, Left, Top, Bottom, or Floating.
	Rotate 90°	Rotates the display 90° clockwise. Applies cumulatively. Die coordinates are unaffected.
	Flip horizontal	Mirrors the display left/right. Die coordinates are unaffected.
	Flip vertical	Mirrors the display top/bottom. Die coordinates are unaffected.
	Zoom mode	Click and drag to draw a zoom region.
	Zoom in	Zooms in one step.
	Zoom out	Zooms out one step.
	Reset zoom	Returns the map to the default fitted view.
	Pan mode	Click and drag to pan the map.
	Box select	Click and drag to select a rectangular group of dies (see Section 4.3).
	Expand	Opens the map full-screen in a modal overlay. Press Esc or click outside to close. Useful for detailed inspection without changing the main view.
	Save image	Downloads the current map view as a PNG. Captures the canvas as displayed, including all active overlays and the legend.
	Summary panel	Opens or closes the summary panel (see Section 6).
	User guide	Opens this guide.

Highlight bin — in bin modes, click any bin swatch in the legend to highlight that bin and dim all others. Click again to clear. Useful for isolating a specific failure category across the wafer.

Bin 2 (Fail) highlighted — all other bins are dimmed.

Overlays¶

Use the Overlays menu to toggle optional display layers on and off:

• XY axis indicator — shows X and Y axis lines through the wafer centre
• Ring boundaries — concentric ring divisions that match the spatial analysis zones
• Quadrant lines — divides the wafer into N, S, E, W quadrants
• Die coordinate labels — draws the (x, y) grid position inside each die (useful at high zoom)
• Reticle grid — stepper field grid (only shown when reticle geometry is configured)
• Colour by spec — pass/fail colouring for Test Value mode when spec limits are defined

Ring boundaries, quadrant lines, and XY indicator all active.

Keyboard shortcuts¶

Gallery¶

The gallery control bar applies to all cards simultaneously.

	Control	Description
	Plot mode	Switches the plot mode for all cards.
	Overlays	Toggles display layers for all cards simultaneously.
	Colour scheme	Switches the colour palette for all cards.
	Orientation	Opens the rotate/flip controls, applied to all cards.
	Columns	Sets the number of columns in the card grid.
	Save image	Downloads the full gallery grid as a single PNG.
	Summary panel	Opens or closes the lot-level summary panel.

Click any gallery card to expand it to a full single-wafer view with the complete single-map toolbar.

4. Interacting with dies¶

4.1 Hover¶

Hovering over a die shows a tooltip with:

• Die grid coordinates (x, y)
• Hard bin and/or soft bin (with name, if named)
• Test values for all loaded tests
• Retest count if the die was probed more than once

4.2 Zoom and pan¶

Scroll to zoom in and out. Click and drag to pan when in Pan mode. The toolbar also provides dedicated Zoom mode (drag to draw a zoom region), Zoom in, Zoom out, and Reset zoom buttons. Tooltips and die selection remain accurate at all zoom levels.

4.3 Box select¶

Switch to Box select mode in the toolbar, then click and drag to draw a selection rectangle. The application may display statistics or details for the selected dies. This is useful for comparing a sub-region against the full wafer. Use Ctrl / Cmd + click to add individual dies to the current selection. Press Esc to clear.

A block of dies near the centre is shown pre-selected. Choose Box select in the toolbar and drag to make your own selection, or Ctrl/Cmd + click individual dies.

5. Findings panel¶

When spatial analysis has been run, the Findings panel lists statistically detected patterns on the wafer. Open it from the toolbar.

Each finding shows:

• Severity — Unusual, Notable, or Info (ordered most to least significant)
• Description — plain-language summary of what was detected and where
• Click to highlight — clicking a finding highlights the affected dies on the map in amber

Severity reflects how strong the statistical evidence is. Unusual findings have both a very low adjusted p-value and a large effect size — they are reliably important. Notable findings are statistically significant with a meaningful effect but not as extreme. Info findings pass the significance threshold at lower strength and are worth reviewing but may reflect smaller or noisier patterns.

Findings panel open showing a detected edge-ring pattern. Click any row to highlight the affected dies on the map.

A failure cluster finding: affected dies highlighted in amber.

Finding types¶

Which finding types are active depends on the application's analysis configuration.

When a spatial pattern classification is detected alongside supporting regional findings (ring, quadrant, sector), the panel groups them together — the pattern classification is the primary finding and the regional findings provide supporting detail.

6. Summary panel¶

The summary panel shows statistics and metadata for the current wafer or lot. Open it from the toolbar.

The summary panel open alongside a single wafer, showing yield, bin breakdown, and per-test statistics. Click any finding to highlight the affected dies.

For a single wafer, the panel shows:

• Wafer and lot metadata (lot ID, wafer ID, test date — when available)
• Total die count, yield %, and counts of pass, fail, and edge-excluded dies
• Hard bin and soft bin breakdown with percentages
• Per-test descriptive statistics (min, max, mean, std dev, median) when test data is loaded
• Spec yield per test when limits are defined — pass die count and yield % split by below-limit and above-limit fails
• Findings list — same findings shown in the Findings panel; click to highlight

A Summary report button (when present) opens a printable full-detail report in a new window or tab. The report contains everything shown in the panel — yield, bin breakdown, ring and quadrant statistics, per-test statistics, and the full findings list — and can be saved as a PDF from your browser's print dialog.

For lot-level views (gallery), the panel shows:

• Lot metadata and wafer count
• Per-wafer yield trend
• Lot-level aggregate bin breakdown
• Cross-wafer comparison findings

7. Lot-stack maps¶

A lot-stack map combines multiple individual wafer results into a single composite view. The display clearly identifies this: the number of wafers included and the aggregation method in use are shown in the panel header (for example, "3 wafers · mean") so you know you are not viewing a single wafer's data.

Individual die coordinates are preserved. For each die grid position, results from all wafers are aggregated into a single value or bin count according to the selected aggregation method.

Stacked plot modes¶

Switching to a stacked mode changes what each die's colour represents:

Aggregation method¶

In Stacked Test Values mode, use the Aggregation method toolbar button (Σ) to choose how values from each wafer are combined at each die position:

Gallery stacked modes¶

In a gallery, stacked modes are always available in the control bar. Switching to a stacked mode shows one card per bin category or per test parameter, aggregated across all wafers in the gallery.

Stacked Hard Bins mode: each die position is coloured by how many wafers had bin 1 (Pass) or bin 2 (Fail) at that location.

8. Reticle overlay¶

When reticle (stepper field) geometry is configured, the Reticle grid overlay draws the stepper field boundaries on the wafer. Each rectangle represents one exposure field from the lithography stepper — the group of dies exposed in a single step. This lets you correlate failure patterns with specific reticle positions — useful for identifying stepper field signatures, alignment drift, or mask defects.

Reticle-position findings in the Findings panel highlight the specific field positions that show elevated failure rates.