Chip art, also known as silicon art, chip graffiti or silicon doodling, refers to microscopic artwork built into integrated circuits, also called chips or ICs. Since ICs are printed by photolithography, not constructed a component at a time, there is no additional cost to include features in otherwise unused space on the chip. Designers have used this freedom to put all sorts of artwork on the chips themselves, from designers’ simple initials to rather complex drawings. Chip graffiti is sometimes called the hardware version of software easter eggs.
Chip art refers to microscale artwork that is printed in integrated circuits. When chips are designed and laid out, sometimes there are empty spaces that are not taken up by buses and other components; chip designers often take the liberty to use the empty spaces to add their own signature or other images, ranging from simple initials to more rather complicated drawings.
Chip art involves the inclusion of images and other icons or signatures into the negative (mask) of a chip that will be etched into a silicon wafer via photolithography. Given the microscopic size of the parts of the chips, chip art cannot be seen without a microscope, and the fact that the designers did not advertise that they added something extra or an Easter egg to certain chips means that there are a number of undiscovered chip artworks out there.
Integrated Circuits are constructed from multiple layers of material, typically silicon, silicon dioxide (glass), and aluminum. The composition and thickness of these layers give them their distinctive color and appearance. These elements created an irresistible palette for IC design and layout engineers.
The creative process involved in the design of these chips, a strong sense of pride in their work, and an artistic temperament combined compels people to want to mark their work as their own. It is very common to find initials, or groups of initials on chips. This is the design engineer’s way of “signing” his or her work.
Prior to 1984, these doodles also served a practical purpose. If a competitor produced a similar chip, and examination showed it contained the same doodles, then this was strong evidence that the design was copied (a copyright violation) and not independently derived. A 1984 revision of the US copyright law (the Semiconductor Chip Protection Act of 1984) made all chip masks automatically copyrighted, with exclusive rights to the creator, and similar rules apply in most other countries that manufacture ICs. Since an exact copy is now automatically a copyright violation, the doodles serve no useful purpose.
In 1984, the U.S. Congress passed the Semiconductor Chip Protection Act. Pre-1984, graffiti was the only way to prove copying; the fact that the rest of the mask was identical was not sufficient proof. After 1984, an identical copy of a mask’s working parts was an automatic copyright violation, and graffiti served no useful purpose.
Chip designers have often etched whimsical imagery onto their creations, but as automated tools improved and design cycles shrank, so did companies’ tolerance for the improvised extras
Because of the hidden nature of chip art, its existence did not become public knowledge until photographer Michael Davidson accidentally stumbled upon it while photographing the geometric patterns of microchips in 1998. The Smithsonian Institution now has a large collection of chip art, thanks to Davidson and other contributors such as Chipworks, a provider of reverse engineering services.
Mike Davidson knows art when he sees it. But he didn’t expect to see it on a microchip. To make the circuitry “pop” for a more richly detailed photo, he lit large areas of the chip with a tungsten-halogen light and increased the magnification to 600X. Suddenly, he saw a face.
What started out as a serendipitous discovery became a passion for Davidson. He began looking for and collecting images he found on other chips and putting them on what he now calls the Silicon Zoo portion of the Molecular Expressions Web site. As word about the site got around, design engineers from all over sent Davidson chips and wafers, hoping to preserve their silicon creatures for posterity. Now the Zoo features the ersatz Waldo along with 300 other pieces of what is variously termed chip art, artifacts, or graffiti.
The images include everything from chip designers’ names, renderings of favorite pets, cartoon characters like Dilbert, and planes, trains, and automobiles. These images are fabricated along with the transistors and interconnects on one or more metal layers overlying a silicon wafer. First, the image is drawn on a mask used to make a pattern in photoresist overlying a metal layer, usually the first. Through the gaps in the mask ultraviolet light is shone onto the photoresist, hardening what it exposes. A solvent washes away the soft remainder, exposing areas of aluminum to etching in their turn. Lastly, the hardened photoresist is washed off with acid, leaving an image in metal.
Many of the creatures housed in the Silicon Zoo Davidson found on small-run video and graphics chips dating from the late 1970s and early 1980s. Back then chip graffiti was more abundant, in part because it thwarted illegal copying, said Louis Scheffer, a former chip designer with Hewlett-Packard Co. and now a fellow at Cadence Design Systems Inc., San Jose, Calif. If someone stole the chip design by simply copying the masks, the graffiti would be copied, too, and give the thief away.
Often this creative artist’s instinct extends to the inclusion of small pictures or icons. These may be images of significance to the designers, comments related to the chip’s function, inside jokes, or even satirical references. Because of the difficulty in verifying their existence, chip art has also been the subject of online hoaxes (e.g. the never-seen “bill sux” comment on a Pentium chip—the reputed “photo” showing the inscription is a hoax).
The mass production of these works of art as parasites on the body of a commercial IC goes unnoticed by most observers and is discouraged by semiconductor corporations, primarily from the fear that the presence of the artwork (which is clearly unneeded) will interfere with some necessary function in the chip or design flow.
Some laboratories have started collaborating with artists or directly producing books and exhibits with the micrographs of these chips. Such is the case of Harvard chemist George Whitesides, who collaborated with pioneer photographer Felice Frankel to publish On the Surface of Things, a highly praised photography book on experiments from (mostly) the Whitesides lab. Also, the laboratory of Albert Folch (who, perhaps not coincidentally, works in BioMEMS, the same field as George Whitesides) at the University of Washington’s Bioengineering Dept. has a highly popular online gallery with more than 1,700 free BioMEMS-related chip art micrographs and has already produced three art exhibits in the Seattle area, with online sales.