How to Use GdsViewer to Inspect and Debug GDSII DesignsGdsViewer is a lightweight, focused tool for viewing and inspecting GDSII layout files. Whether you’re a layout engineer, verification engineer, or a student learning IC design, GdsViewer helps you quickly visualize geometric data, check connectivity, and spot layout issues before manufacturing. This article walks through installing GdsViewer, opening GDSII files, navigating and annotating layouts, performing common inspection tasks, debugging typical layout problems, and integrating GdsViewer into a verification workflow.
What GdsViewer is best for
GdsViewer is designed primarily as a fast renderer and inspector for GDSII (also called GDS2) files. It excels at:
- Rapid visualization of large GDS files without long load times.
- Layer-based inspection to view, hide, and colorize layers.
- Hierarchy navigation to explore cells and instances.
- Quick measurement and simple geometry queries for manual debugging.
It is not a full-featured layout editor; GdsViewer focuses on viewing, checking, and annotating rather than modifying layout geometry.
Installation and setup
- Download GdsViewer from the official distribution (binary or source). Check compatibility with your OS (Linux, macOS, Windows).
- Install any required dependencies (for source builds, typically a C++ toolchain and graphics libraries).
- Launch the application or binary. Optionally, set up file associations so GDSII files open with GdsViewer by default.
Tip: If you’ll inspect very large layouts, run GdsViewer on a machine with adequate RAM and a decent GPU to speed rendering.
Opening and exploring a GDSII file
- Use File → Open (or drag-and-drop) to load a .gds or .gdsii file.
- GdsViewer typically loads cell (structure) hierarchy on the left pane. Click a cell name to display it.
- Zoom with mouse wheel or gestures; pan with middle-button drag or click-and-drag depending on platform.
- Use “fit” or “zoom to selection” to quickly center an area of interest.
Hierarchy tips:
- Expand and collapse instances to understand how top-level cells compose instances of lower-level cells.
- Use flattening or “show composed” modes if you need to inspect the effective geometry after instance transforms.
Layer management
Layer control is one of the most powerful features for inspection:
- Each layer in GDSII has a layer number and data type. GdsViewer shows a list of detected layers.
- Toggle visibility per layer to isolate structures (e.g., show only metal1, or only diffusion).
- Assign colors to layers to make adjacent layers visually distinct.
- Use opacity controls to make underlying layers visible beneath others.
Examples of useful layer combinations:
- Poly + diffusion + contact — to inspect transistor active areas.
- Metal1 + via + metal2 — to check routing continuity and via placement.
- Implant/Well + active — to verify well ties and implants align correctly.
Basic measurement and inspection tools
GdsViewer provides measurement and query tools needed for manual debugging:
- Distance/length ruler: click two points to measure the Euclidean distance. Useful for DRC-relevant spacings.
- Area measurement: select a polygon or region to compute area for density checks.
- Snap-to-grid options and coordinate display in the status bar for precise inspection.
- Selection tool: click or box-select shapes to see their layer, datatype, bounding box, and cell origin.
Coordinate systems:
- GDS files use layout units; GdsViewer reports coordinates in user units. Confirm unit settings (database units and user units) to ensure measurements match design rules.
Searching and cross-probing
- Name search: find cells by name (wildcard support often available).
- Instance search: locate instances by their hierarchy path.
- When double-clicking an instance, use “go to definition” to open the referenced cell and “show instances” to highlight where a cell is instantiated.
- Cross-probing between the hierarchy tree and viewport helps you keep context when navigating large designs.
Annotations and markups
For collaboration and review:
- Add text notes and markers to highlight issues (missing contacts, antenna points, DRC hotspots).
- Export annotated screenshots or save session states that preserve view and annotation layers for teammates.
- Use different marker colors to indicate severity or issue type.
Debugging common layout problems
GdsViewer helps spot and triage many typical layout issues before running full P&R or DRC:
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Missing or misaligned contacts/vias
- Zoom to routing intersections and inspect layer overlays (e.g., metal and via layers).
- Toggle via and metal layer visibility to confirm a via sits at the correct intersection and that overlap rules are met.
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Spacing violations (DRC hot spots)
- Use the ruler and snap grid to measure separations between polygons/edges.
- Look for narrow necks in wires or small spacing pockets between adjacent shapes.
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Wrong cell instantiation or incorrect transforms
- Check the instance transform matrix (rotation/scale/mirror) reported by the instance properties.
- If an instance appears flipped or rotated unexpectedly, verify its transform and the original cell orientation.
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Missing or broken hierarchy links
- If an instance appears empty, confirm the referenced cell exists in the same GDS file or in included libraries.
- Use the search to locate duplicate or shadowed cell names that might cause the wrong cell to be instantiated.
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Density and antenna concerns
- Inspect implant and diffusion coverage relative to metal routing.
- Use area measurements and layer overlays to find metal density imbalances or long, unbroken interconnects.
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Label and pin visibility
- Verify text labels and pin markers are on the expected layers and not occluded by opaque layers.
- Toggle text layers to confirm pin names and orientations.
Exporting views and data
- Export selected regions as GDS chunks if you need to hand off a snippet to another tool.
- Save high-resolution PNG/SVG exports of the viewport for reports or bug tickets.
- Export a text listing of instances and shapes (when supported) to script-based checks or logs.
Integrating GdsViewer into a verification workflow
- Use GdsViewer for an initial visual sanity check before running time-consuming DRC/LVS.
- Combine quick visual inspection with automated checks: when a verification tool flags a net or DRC hotspot, open that region in GdsViewer for manual validation and triage.
- Keep a shared session directory or annotated exports for handoffs between layout and verification teams.
Workflow example:
- Run DRC/LVS → get list of flagged coordinates.
- Open flagged coordinates in GdsViewer via “go to coordinate” and visually inspect.
- Annotate and capture screenshots; assign severity and owner.
- Export region or cell and send to layout engineer for correction.
Tips and best practices
- Always confirm units: mismatch between assumed units and actual GDS units is a common source of measurement errors.
- Use layer color schemes that match your foundry’s documentation to speed recognition.
- Keep the hierarchy tree open and use search filters to jump between cells quickly.
- For collaborative reviews, standardize annotation colors and marker conventions.
- When dealing with very large files, use flatten/view-scope or load-on-demand options if available.
Limitations and when to use other tools
GdsViewer is optimized for inspection, not editing or full verification. For these tasks use:
- A layout editor (e.g., KLayout, Cadence Virtuoso, Mentor Graphics) for geometry editing and correction.
- DRC/LVS tools for automated rule checking and electrical verification.
- Extraction tools for parasitic/resistance-capacitance analysis.
Quick checklist for pre-fab review with GdsViewer
- Confirm GDS unit settings match design intent.
- Verify critical layer stacks and via placements.
- Measure and validate spacing in critical areas.
- Inspect hierarchy for unintended flattened or missing instances.
- Annotate and export hotspots for fixes.
GdsViewer is a practical, focused tool for rapid visual inspection and debugging of GDSII designs. Used as the first line of review it saves time by letting engineers catch glaring issues quickly, document them, and hand off precise regions to full-featured editors and automated verification tools.
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