HISTORY OF THE PROFESSION

HISTORY OF THE PROFESSION

During the past two decades, the electronics industry has grown very fast both in size and in complexity. Designers began talking about chip design only 25 years ago. At the beginning, the idea was to design chips to reduce the computer size. Instead of room-sized computers, we have now ended up with PCs running at a speed that back then was considered “impossible to imagine.” The application of IC technology has exploded into many parts of our lives.

IC layout design was originally hand-drafted on special paper called Mylar. This was a long and laborious task. The market demands and advances in technology brought about an immediate need to develop software and hardware solutions to improve the time-to-market of the chip designs and especially to automate the entire process. Accuracy of the final masks was also a driving force in the computerization of layout design.

The first platforms were custom built to ensure that graphics applications ran quickly and had sufficient capabilities. Companies such as CALMA (Data General) built mainframe-sized machines and developed specialized software for printed circuit board (PCB) and integrated circuit (IC) applications.

The disk size was huge by today’s standards. The top-of-the-line computer had 220 MB of disk space and only 0.5 MB of DRAM was available at the time. The price tag was around $1 million U.S., and not everybody could afford to be involved in this kind of design. As the market and the chip sizes grew and more companies were involved in chip design, the hardware and software developers came up with faster, smaller, and cheaper solutions.

The biggest revolution in hardware was the development of the “engineering workstation,” which ran a version of the UNIX platform. Workstations have developed over the years to incredible speed and complexity. They are used for all kinds of engineering design, so the prices are very affordable. HP, Sun, and IBM are only a handful of survivors in this field, Daisy being one that has disappeared from the market. Today there is tremendous pressure to go to even cheaper and more popular platforms, such as PCs with Linux and Windows NT platforms.

As the hardware platforms evolved, software development progressed at an even faster rate. Companies such as Mentor Graphics, Cadence, Compass, and Daisy gained larger and larger shares of the IC and PCB design tools market. For the PC platform, a company such as Tanner, with a product called L-Edit, is an example of how the software development market has grown for IC design (more details are given in Chapter 10).

The direction for development of the software has really been toward more and more automation of the tasks that are labor intensive: for example, designs with hundreds of transistor blocks, where interconnection analysis is impossible to do by human eyes, or verification of a 256-MB memory chip (more details in Chapter 10).

Significant examples of automation include the following:

Layout synthesis: Layout can be created from “code” instead of the traditional methods of manually drawing the polygons.

Layout migration: Alternatively, layout can be “migrated” from one set of design rules to another using mapping and sophisticated compaction techniques.

Layout verification: These tools perform an increasing number of checks on the final layout before it goes to production. For example, minimum size rules are checked to ensure that the design is manufacturable.

Circuit synthesis: Similar to layout synthesis, in this case schematics can be automatically generated from specialized “code” (i.e., VHDL or Verilog). This has had a huge impact on layout design, as the sheer volume of circuitry produced by these circuit synthesis tools created a need for more layout automation such as place-and-route tools.

Place-and-route: Instance placement for literally millions of cells as well as optimizing the placement for minimum connectivity and maximum circuit performance.

Today, layout design is carried out in an environment that is ever changing. The software tools and approaches, computing platforms, the companies providing these tools, the customers we serve, the applications that are being implemented, and the market pressures we face are all changing year by year.

These changes make this industry an interesting one in which to be involved. However, let’s not forget that the fundamental concepts behind producing quality layout are based on physical and electrical properties that never change. This is the basic principle on which this book was written.