Designing Your Own Chip

Introduction

• Overview of designing a chip.
• Process and steps required.
• The democratization of chip design using open-source tools and resources.

Essential Tools and Resources

• Skywater 130 PDK: A key enabler, opened by Google, allows for open access to the manufacturing process of chips.
• Tiny Tapeout: A platform that enables individuals to design and get their own chip manufactured at a low cost.
• Virtual Machine: Contains all necessary tools—available for free download.

Process Overview

Designing the Chip

1. Schematic Capture (Xschem): Design circuits, set parameters for components like transistors, resistors, etc.
2. Simulation: Using NGSpice to simulate the design before moving to the layout stage.
3. Layout (Magic): Convert schematic into physical design, considering all manufacturing rules and parasitic effects.

Testing and Verification

• Post-Layout Simulation: Ensure the design with real parasitic components behaves as expected.
• LVS (Layout vs. Schematic): Confirm that the layout matches the original schematic to avoid fabrication errors.
• DRC (Design Rule Checking): Validate design rules to ensure manufacturability.

Manufacturing Process

1. Tiny Tapeout Process:

   • Reserve space on a multi-project wafer (MPW).
   • Submit design files through GitHub, ensuring all checks pass.
   • Production managed by eFabless & Skywater.

2. Costs:

   • Entry-level costs have reduced significantly: from hundreds of thousands to a few hundred dollars.
   • Options available for educational institutions to reduce costs by sharing demo boards.

Practical Example

Designing an Inverter

1. Creating the Schematic:
   • Add necessary components: pfet, nfet, input/output pins.
   • Wire components accordingly.
2. Simulating the Inverter:
   • Spice configuration: add the necessary voltage sources and run transient analysis.
   • Analyze waveform results.
3. Creating Layout:
   • Import netlist into Magic for layout.
   • Route connections and run parasitic extraction.
4. Verification:
   • Run LVS to ensure the layout matches the schematic.
   • Perform post-layout simulation to compare behavior with schematic simulation.

Submission to Tiny Tapeout

1. Creating the GDs File:
   • Export the design in GDs format from Magic.
2. Uploading to GitHub:
   • Use the Tiny Tapeout GitHub template for submission.
   • Ensure all GitHub actions/checks pass before final submission.
3. Manufacturing and Receiving Chips:
   • Wait for the MPW process to complete (7 months cycle).
   • Chips are then distributed to participants.

Additional Notes

• Educational Advantage: Opportunity for schools and universities to participate at lower costs by sharing resources.
• Opensource and Community Support: Access to a robust community via Discord and other forums, providing collaboration and troubleshooting help.
• Future Prospects: Increasing ease of access to chip design likely to lead to an explosion in innovation, similar to what happened with PCBs.

Links & Resources

• Tiny Tapeout: Main platform for chip design and submission.
• Psychogenic Technologies: Co-founded by Pat Degan, provides extensive resources and expertise.
• Xschem: Schematic capture tool.
• Magic: Layout tool.
• NGSpice: For circuit simulation.