Electronic Design Automation and the Design of Integrated Circuits Abstract
A circuit, simply put, is defined as a complete path around which an electric current can flow in order to complete a predesigned task. Circuit design is the intermediate process by which electrical circuits are moved from the specification stage - where the circuit’s purpose is determined - to the production stage, where all of the information necessary to build a working circuit is ready for implementation. In order to keep up with demand for consumer electronics, a fast and efficient way to design and construct the myriad types of circuitry must be in place. This essay will illustrate the basics of circuit design and describe the automated circuit design process.

Electronic Design Automation
In a large part of the world, electronics are a mainstay of modern society. In the beginning, electronics were much more simple in design, but with the caveat of being much larger today: in the 1980s cellular phones weighed upwards of two pounds and were about three times the size of modern cell phones. Over time, as electronics became smaller and as demand for them increased, a way to design and construct smaller and more efficient circuits became necessary. Enter Electronic Design Automation.
An electric circuit is an electrical path that provides a path for an electrical current to flow. While it may seem like a simple matter to design and construct a circuit, the process has become quite intensive, requiring delicate machinery and precise design flows. A circuit consists of several components, each performing a specific task: transistors are used to amplify and switch electrical signals; capacitors store electricity until it is needed; resistors offers electrical resistance in order to maintain a specific charge and switches complete or break a circuit by either interrupting the electrical current powering it or else diverting it to other circuits. As circuits become more and more complex, technology has been able to package them into smaller and smaller containers, culminating in the integrated circuit (IC) found in almost all electronic devices, ranging from wristwatches and cellular phones to the largest aircraft carriers.
Obeying Moore’s law, which states that transistor performance and density double every 3 years (Packan, 2013) becomes more difficult to do by hand. As integrated circuits become smaller and smaller, it has become necessary to rely on automation to attain the high level of precision needed to construct the delicate circuitry in today’s electronics where it had previously been done by hand. This is called Electronic Design Automation.
Electronic design automation (EDA) is a discipline by which software is used to design and implement electronic systems such as integrated circuits. The process by which this is accomplished is many times more precise than the older methods where circuits were designed and laid out by hand (Brayton & Cong, 2009).
There are several steps in designing and building an integrated circuit. The first is to design the circuitry on a software platform using Hardware Description Language (HDL), which is a computer language used in designing the structure and operation of the circuit.
The second step in designing the circuit is to generate the necessary logic gates with the EDA app. A logic gate is a device within the IC that uses Boolean logic to test one or more inputs in order to arrive at a logical output which is used to map the actions performed by the integrated circuit. It is necessary to map the actions of the entire integrated circuit before implementation in order to ensure that the layout of the circuit is correctly implemented in manufacture once testing is complete.
The next step is to ensure that the IC is testable. Testing the circuit is crucial to the successful manufacture of a new circuit design to avoid the manufacture of defective chips, leading to millions of dollars in wasted materials. Testing the circuit involves millions of individualized tests to verify that each of the thousands of logic gates and the permutations thereof each lead to the correct outcome. Once the testing of the IC is complete, manufacture of the design can commence. These first three steps comprise the logical design implementation phase of the circuit design flow. The testing phase stands alone in the design flow, a signal of the importance of that stage.
The manufacture of an integrated circuit has multiple stages, and in manufacturing integrated circuits of the size required in turn requires the most precise mechanical means of building them. First, the circuit has to be laid out using the circuit design platform. This stage is an extension of stage two, where the logic gates and other circuit hardware designed in the software schematic are now positioned into the physical design. Next the layout is verified using more software simulations against the design of the circuit. This is the final stage in which discrepancies or flaws can be found and eliminated before the mass production of the integrated circuits begins.
The physical building of an integrated circuit from raw silicon into a fully functional circuit has several stages; here is a brief description of each:
1. A giant silicon crystal is grown in a tank using a seed crystal and slowly rotating it in a silicon bath until a uniform silicon crystal is formed. It is then polished cylindrical crystal about 300 mm in diameter and about 9-12 inches in height.
2. The giant silicon crystal is then sliced into individual wafers, each one polished on either side to a high shine. About seven hundred integrated circuits can be made from each wafer.
3. Each side of the wafer is coated with a proprietary photosensitive material which hardens when exposed to light.
4. The circuit that was designed with the EDA platform is then etched into a stencil for embedding into the silicon wafer.
5. The stencil is held over the wafer and a light is shone through it onto the coated wafer, causing the coating that is exposed to the light to harden. Those areas not exposed to the light remain pliable.
6. The wafer is then dipped into an acid bath to remove those parts of the photosensitive coating that remain pliable.
7. The entire process is repeated many times for each wafer: recoating with photosensitive material, creating different stencils for each layer of the integrated circuit, and then the hardening of the material and removal of the unneeded portions. This is repeated until the integrated circuit is complete, with many circuits on each wafer.
8. Finally, the chips are cut from the wafers and inserted into individual plastic or ceramic casings. The end result is the common microchip.
Currently, the semiconductor business is valued at about $292 billion (Rosso, 2013). With the current demand for electronics, and by extension microchips, the need to quickly and efficiently produce enough integrated circuits to satisfy that demand becomes obvious. The role of Electronic Design Automation is crucial to the industry both now and in the future.
The EDA industry is always striving to find new ways to design microchips. A new technology called Systems on a Chip (SoC) is now being developed which integrates all the components of a computer or other electronic device onto a single chip. Mass-producing these SoCs will prove to reduce costs of manufacturing and reduction of waste. It is in this way, and others such as solving current design issues that Electronic Design Automation is helping the semiconductor industry to grow larger than ever before.

Works Cited
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Packan, P. A. (2013). Pushing the Limits. Science, 2079.

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Rosso, D. (2013, February 4). Semiconductor Industry Posts Near-Record Sales Total in 2012.

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