Physical design is a crucial step in the chip design process and involves the transformation of the abstract design into a physical layout, which is used to create the masks for photolithography
The goal of physical design is to take the abstract design and map it onto the silicon wafer in a way that meets all the design requirements, such as performance, power, and area constraints. This requires careful planning and optimization of the placement of transistors, interconnects, and other components on the silicon wafer
Physical design involves several steps, including
- Floorplanning: This is the first step in physical design, and it involves creating a high-level layout of the chip, including the placement of major blocks and the allocation of space for different components.
- Placement: In this step, the individual transistors and other components are placed on the silicon wafer. This step is critical for ensuring that the chip meets performance and power constraints, as well as for minimizing the total area used by the chip
- Routing: In this step, the interconnects between the components are created. This step is critical for ensuring that the chip meets performance and power constraints, as well as for minimizing the total area used by the chip.
- Parasitic extraction: In this step, the parasitic elements, such as resistance and capacitance, are extracted from the physical layout and incorporated into the simulation models used in verification
- Layout versus schematic (LVS) verification: In this step, the physical layout is compared to the original design to ensure that it meets the specifications and requirements
- Design rule checking (DRC): In this step, the physical layout is checked against a set of design rules to ensure that it meets the fabrication requirements
Physical design is a complex and time-consuming process that requires a strong understanding of semiconductor technology and photolithography, as well as expertise in areas such as computer-aided design (CAD) and optimization algorithms. Physical designers use specialized tools, such as physical design automation (PDA) software, to aid in the creation of the physical layout