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 switch to a pass/fail view, use the Spec pass/fail or Test pass/fail option in the Overlays menu (available when spec limits are defined, or a recorded verdict exists, for the active test).

Spec pass/fail mode replaces the colorbar with a small spec legend: Pass, Fail high, and Fail low swatches (only the categories that apply to the test's limits) with a die count beside each. This judges dies against the test's spec limits (limitLow / limitHigh).

Test pass/fail mode replaces the colorbar with a Pass / Fail legend and die counts, coloured by the tester's own recorded verdict for that test — not a spec-limit judgement. A test with no measured value (a functional, go/no-go test) always displays this way; selecting it switches the map into Test pass/fail automatically, since there is nothing to plot on a gradient.

Every map also shows a short title by the colorbar or legend naming what is displayed — the test name (and number, in spec mode), the bin type, or the stacked wafer count.

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. This affects only the colorbar's range, never how out-of-spec dies are shown. In both ranges every die is coloured by the gradient so you can read the value distribution, and out-of-spec dies are marked with a triangle — pointing down (▽) for below LSL, up (△) for above USL — so they stand out without leaving the distribution. The triangle is drawn black or white per die for contrast against its own colour, so it stays visible under any colour scheme, and its shape (not colour) carries the below/above-limit meaning.
• Spec pass/fail: 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. A spec legend replaces the colorbar, listing each applicable category with its die count.

Some tests have no measured value at all — a continuity check or any other go/no-go test, where the only result is a recorded pass or fail. Selecting one of these functional tests as the active test switches the map into Test pass/fail automatically: a Pass/Fail legend by die count, coloured by the tester's own recorded verdict rather than a spec-limit judgement (there is no gradient to fall back to). Test pass/fail is also available as an Overlays option on an ordinary parametric test when it carries recorded verdicts, as an alternative to spec-limit judgement.

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), Spec pass/fail (Test Value mode with limits), and Test pass/fail (Test Value mode, active test is functional or has recorded verdicts).
	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. Hidden whenever a pass/fail display is active or the active test is functional.
	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).
	Insights	Swaps the map for this wafer's own chart suite — yield, bin breakdown, process capability, and more (see Section 8). Only shown when the application has enabled it.
	Expand	Opens the map in an enlarged modal overlay. A maximise button in the modal grows it to fill the window (or press F). Press Esc or click outside to close. Useful for detailed inspection without changing the main view. Hidden while the Insights tab is open — each chart inside Insights has its own expand button instead.
	Save image	Downloads the current map view as a PNG. Captures the canvas as displayed, including all active overlays and the legend.
	Findings	Opens or closes the Findings sidebar (see Section 6).
	User guide	Opens this guide.

This guide's own window (and a gallery card detached into its own window, see Section 3 — Gallery below) is a floating window, not a modal — its header shows minimize, maximize, and close buttons, and it can be dragged and resized by its corner grip. Minimizing collapses it to a small title strip without closing it; click it again to restore.

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)
• Spec pass/fail — pass/fail colouring for Test Value mode, judged against spec limits, when the active test defines them
• Test pass/fail — pass/fail colouring for Test Value mode, coloured by the tester's recorded verdict; always on for a functional (no measured value) active test

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.
	Findings	Opens or closes the lot-level Findings sidebar.
	Insights	Swaps the grid for a lot-wide chart suite — yield, bin breakdown, process capability, and more (see Section 8). Only shown when the application has enabled it.

Click a card's expand button to detach it into its own separate window with the complete single-map toolbar (falls back to a floating window inside the page if separate windows aren't available in your environment). The vacated grid card becomes a placeholder whose own button reattaches it; closing the detached window does the same.

4. Interacting with dies¶

4.1 Hover¶

Hovering over a die shows a compact tooltip. It always includes the die grid coordinates (x, y), and a retest count if the die was probed more than once. The rest depends on the active plot mode:

• Bin modes — the die's bin verdict (number and name, if named), plus a note of how many test values are recorded for the die
• Test Value mode — the active test's value in bold, flagged when it is out of spec, with the remaining tests summarised as "+N more tests"
• Stacked modes — the single aggregated value or count at that position

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 with a black-and-white outline, visible against every colour scheme

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 with a white-and-black outline.

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. Findings sidebar¶

The Findings sidebar shows detected anomalies for the current wafer or lot, always docked next to the map so a clicked finding can highlight the affected dies right there. Open it from the toolbar. Severity, kind, and region filter controls at the top of the sidebar narrow the list down.

The Findings sidebar open alongside a single wafer. Click any finding to highlight the affected dies; use the filter controls to narrow by severity, kind, or region.

Yield, bin breakdown, ring/quadrant regional yield, and per-test statistics — previously shown in this same panel — now live in the Insights tab's Overview sub-tab instead, since that content doesn't need the map on screen the way a finding's highlight does.

A Summary report button (when present) opens a printable full-detail report in a new window or tab, still covering everything findings-adjacent — 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 sidebar shows lot-level findings by default, with a Wafers tab listing every wafer that has its own per-wafer findings — click a row to open that wafer.

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. Insights tab¶

The Insights toolbar button (single map or gallery) swaps the wafer view for a chart suite computed from the same die data — without leaving the toolbar. Click it again to return to the map. Independent of the Findings sidebar (Section 6) — the two toggle independently, and opening one never hides the other's toolbar button, since Findings has nothing to highlight against once the map is replaced.

Insights is organized into three sub-tabs:

• Overview — a yield bar (labelled with the pass bins actually in use), a hard/soft bin pareto, and ring/quadrant regional yield and per-test min/mean/max/spec-yield statistics.
• Distributions — process capability (Cp/Cpk/Pp/Ppk for tests with both a lower and upper spec limit; tests missing a spec still appear, normalized onto their own range and sorted by variability), a test-value box plot, and a value histogram. Clicking a capability box drives the box plot and histogram onto that same test automatically.
• Correlation — a test-to-test correlation matrix and a die-level scatter plot. Clicking a matrix cell drives the scatter plot onto that pair.

In a gallery with more than one wafer, a Group by control appears whenever wafer metadata (lot, product, test program, temperature, split, or a custom field) actually varies across the loaded wafers — grouping pools or restricts each panel differently depending on what makes sense for that chart type. Histogram, correlation, and scatter also offer a Wafer picker to narrow from "all wafers pooled" down to one wafer at a time. Clicking a yield bar or box-plot row for one wafer opens that wafer's own map — a box-plot click opens directly on the test you were looking at.

Insights tab open on a single wafer, Overview sub-tab: yield and bin pareto, ring/quadrant yield, and per-test statistics — all computed from this wafer's own dies. The Distributions sub-tab has process capability, a test-value box plot and histogram; Correlation has a correlation matrix with scatter plot. In a gallery, Overview also gains a "Group by" control and per-wafer yield/box-plot rows.

Gallery Insights, Overview sub-tab: lot-wide yield by wafer (click a bar to open that wafer's map), hard/soft bin pareto, ring and quadrant yield, and pooled per-test statistics. The "‹ Gallery" tab returns to the card grid.

Distributions sub-tab: process capability (coloured by Ppk — green capable, orange marginal, red poor; tests without spec limits are muted and dashed), a per-wafer test-value box plot, and a value histogram. Clicking a capability box drives the box plot and histogram onto that test.

Correlation sub-tab: test-to-test Pearson correlation matrix (blue = positive, orange = negative; intensity = strength) and a die-level scatter plot coloured by hard bin. Clicking a matrix cell drives the scatter plot onto that pair.

9. 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. Hovering any die also shows its Reticle (column, row) position — its location within its own stepper field — just below the die's coordinate in the tooltip.