Design Closure is a part of the digital electronic design automation workflow by which an integrated circuit (i.e. VLSI) design is modified from its initial description to meet a growing list of design constraints and objectives. Every step in the IC design (such as static timing analysis, placement, routing, and so on) is already complex and often forms its own field of study. This article, however, looks at the overall design closure process, which takes a chip from its initial design state to the final form in which all of its design constraints are met. Introduction Every chip starts off as someone’s idea of a good thing: "If we can make a part that performs function X, we will all be rich!" Once the concept is established, someone from marketing says "To make this chip profitably, it must cost $C and run at frequency F." Someone from manufacturing says "To meet this chip’s targets, it must have a yield of Y%." Someone from packaging says “It must fit in the P package and dissipate no more than W watts.” Eventually, the team generates an extensive list of all the constraints and objectives they must meet to manufacture a product that can be sold profitably. The management then forms a design team, which consists of chip architects, logic designers, functional verification engineers, physical designers, and timing engineers, and assigns them to create a chip to the specifications. Constraints vs Objectives The distinction between constraints and objectives is straightforward: a constraint is a design target that must be met for the design to be successful. For example, a chip may be required to run at a specific frequency so it can interface with other components in a system. In contrast, an objective is a design target where more (or less) is better. For example, yield is generally an objective, which is maximized to lower manufacturing cost. For the purposes of design closure, the distinction between constraints and objectives is not important; this article uses the words interchangeably. Evolution of the Design Closure Flow Designing a chip used to be a much simpler task. In the early days of VLSI, a chip consisted of a few thousand logic circuits that performed a simple function at speeds of a few MHz. Design closure was simple: if all of the necessary circuits and wires "fit", the chip would perform the desired function. Modern design closure