The Secret Art of Chip Graffitti

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nature and told Davidson to look for other images on the chip,including a license plate containing the chip nu mber and its ver-sion [see opposite page, bottom right ph oto].

What started out as a seren dipitous discovery became a pas-sion for Davidson. He began looking for and collecting imageshe found on other chips and pu tting them on what he n ow callsthe Silicon Zoo portion of the Molecular Expressions Web site(http://micro.magnet.fsu.edu/creatures/index.html). As wordabout the site got around, design engineers from all over sentDavidson chips and wafers, hoping to preserve their siliconcreatures for posterity. Now the Zoo features the ersatz Waldoalong with 300 other pieces of what is variously termed chip art,artifacts, or graffiti.

The images include everything from chip designers nam es,renderings of favorite pets, cartoon characters like Dilbert, andplanes, trains, and automobiles. These images are fabricatedalong with the transistors and interconnects on one or moremetal layers overlying a silicon wafer. First, the image is drawnon a mask used to make a pattern in photoresist overlying ametal layer, usually the first. Through the gaps in the mask ultraviolet light is shone onto the photoresist, hardening whatit exposes. A solvent washes away the soft rem ainder, exposingareas of aluminum to etching in their turn. Lastly, the harden edphotoresist is washed off with acid, leaving an image in metal.

Many of the creatures hou sed in the Silicon Z oo Davidsonfound on small-run video and graphics chips dating from the

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Mike Davidson knows art when he sees it. Buthe didn t expect to see it on a microchip.

One day about six years ago, the seniorresearch en gineer was qu ietly working awayin his lab at the National High Magnetic

Field Laboratory at Florida State University, in Tallahassee, tak-ing photographs for his annual chip-shot calendar, which fea-tures microscopic images of microchips. To fit as much of aMIPS R4000 chip as possible into a single photograph, he set hishigh -powered Nikon FX/L optical microscope at a relatively lowmagnification, between 25X and 100X. Then, to make the cir-cuitry pop for a more richly detailed photo, he lit large areas of the chip with a tungsten-halogen light and increased the mag-

nification to 600X. Sudden ly, he saw a face [seeopposite page, bottom left photo].

To Davidson s eye, the preternaturally longmug, roun d spectacles, lumberjack hat, and fly-

away hair looked just like Waldo, the then-ubiq-uitous cartoon character of Where s Waldo? fame. I realizedit wasn t part of the integrated circuitry, Davidson said, but Ithought it might be something the engineers had put on the chipto thwart anybody trying to reverse-engineer it.

Intr igued, he posted photographs of Waldo on h is MolecularExpressions Web site, home to microscopic images of every-thing from beer bottle labels to DNA. Soon after, he was con-tacted by the image s creator, chip designer Kevin Kuhn, whoworked at MIPS Technologies Inc., Mountain View, Calif.

He told me it wasn t really Waldo [but] another designer atMIPS, Davidson told IEEE Spectrum . He said it was just art-

work that he had put on the chip because he had spent su ch alot of his life working on the chip. Kuhn called it a sort of sig-

B Y H A R RY G O L D S T E I NS en i o r As so c i a t e E d i t o r

Chip designers have often etched whimsical imagery onto their creations, but as automated tools improved anddesign cycles shrank, so did companiestolerance for the improvised extras

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The diversity of chip art is revealed by [counterclockwise,from top] a whale on an Allen-Bradley/Rockwell node adapter IC; Hagar of comic strip fame, found on a Nokia cell phone chip; Waldo on a MIPS microprocessor that also sported a license plate with the processors model number and version; and a muscleman from Siemens (now Infineon) on a power controller. The muscleman and Hagar were unearthed by reverse engineers at Chipworks Inc.

TOP & BOTTOM: MICHAEL W. DAVIDSON/FLORIDA STATE UNIVERSITYMIDDLE: CHIPWORKS INC.


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late 1970s and early 1980s. Back then chip graffiti was moreabundant, in part because it thwarted illegal copying, saidLouis Scheffer, a form er chip des igner with Hewlett-PackardCo. and now a fellow at Cadence Design Systems Inc., SanJose, Calif. If someone stole the chip design by simply copy-ing th e m asks, the graffiti would be copied, too, and give thethief away.

But in 1984, the U.S. Congress passed the SemiconductorChip Protection Act. Pre-1984, graffiti was the only way to provecopying; the fact that the rest of the mask was identical was not

sufficient proof. After 1984, an identical copy of a mask s work-

ing parts was an au tomatic copyright violation, and graffiti servedno useful purpose.

In a sense, then, the Silicon Zoo is more like a museum dis-playing relics of a bygone era. In contrast, the silicon art gallery(http://www.chipworks.com/art/silicon_art.htm) maintainedby Chipworks Inc., a reverse-engineering company based inOttawa, features graffiti from recent chips. The cartoon characterHagar, for one, who resembles a Viking warrior, was takenfrom a Nokia cell phone whose die markings date the chip to1999 [see previous page, middle left photo]. According to JuliaElvidge, vice president of marketing and sales, the company sengineers find such art on 1 in 10 of the chips they reverse-engi-

neer and don t believe there has been a significant drop-off.Elvidge agrees that at certain chip-makers graffiti is now harder

to pull off. She attributes the trend to the un fortunate destructionof chips by wayward doodles, accidents that soured many com-panies on extracurricular artifacts. Others believe that chip arthas fallen victim to advances in circuit design automation andcompressed product cycle times.

Kilroy Was HereWhat motivates those who create chip art? Certainly markingyour territory the way wolves do is par t of the m otivation, saidLarry D. Johnson, a one-time MIPS designer who went on to

manage the Crusoe chip project for Transmeta Corp., Santa

Clara, Calif. People are saying, Look! I m here. Announcing your existence with images visible only

through a microscope may seem an obscure route to fame. Infact, though, according to several chip graffiti artists, enlargedimages are often displayed on the walls of people s offices andcubicles as portions of huge pr inted plots of the IC. They arealso visible to the designers who work on revisions of the IC,markers of those who blazed the buses first.

Many of the images are insider jokes that only other design-ers or engineers would get, like puns on the names of chipsor their functions. The first one that former H P chip designerWilly McAllister did was a visual pun on the adder logic cir-

cuits on an arithmetic chip around 1980. We did full addersand half adders, little snakes with full tummies and little

The subjects of chip art run the gamut fromcartoon characters such as Dilbert [oppo-site page, lower right] to Anubis, the jack-

al-headed guide to the underworld of the ancientEgyptians [right]. Early art such as the sailboat[lower right] was as simple as the tools used todraw it. Later renderings, such as the sundial[opposite page, lower middle] and the littleengine that could from a childrens book of thesame name [opposite page, upper right], hadparts drawn on several chip layers. H.G.

A Chip GraffitiGallery

" The SailboatDating from the early 1970s, this is the oldest

piece of graffiti in Mike Davidsons Silicon Zoo.

" Pac-ManHe is chomping gallium arsenideon a silicon germanium RF chipfrom TEMIC Semiconductors.

" Anubis About 100 microns tall, this god was found on a Silicon GraphicsMIPS R12000 microprocessor.

" Full Adder A pun on a logic circuit that sums threebinary bits, this snake made tracks in 1980.

# Mr. TFans at Dallas Semiconductor

put this television personality on their T1 transceiver chip.

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snakes cut in half its pretty juvenile humor, he admitted[see opposite page, far left photo].

McAllister, now manager of the microanalytical technologydepartment in the Life Science Technologies Laboratory atAgilent Laboratories, Palo Alto, Calif., considers his master-piece to be an im age he and h is designers created for a m em-ory controller in 1988. Part of an early microprocessor chip setused in the HP-9000 series computers, the controller s codenam e was Cheetah. So right from the star t, McAllister was onthe lookout for an etchable im age of the fast cat.

The best of all the cheetah im ages that we d found was the

September 1986 cover of IEEE Computer magazine, he remem-bered [see photo, p. 54]. The cheetah was on the run, but thelegs were blurred, so McAllister asked his wife, Monica, agraphical artist, to redraw the picture.

Taking her pencil drawing with him to work, he blew it up ona copier to about a th ird of a meter long and then digitized it, tak-ing turns with his colleagues at hand-tracing it on an electronictablet connected to the compu ter. Such a step would have beenimpossible just two years earlier, when HP designers still usedpencil and paper to architect even 100 000-transistor ICs. Thecheetah tracing m arked the first time McAllister s team wieldedcomputer tools to render a piece of graffiti [again, see p. 55].

The tools certainly helped. Pencil and straight-edge toolshad confined them to drawing only the most primitive images,

such as block letters or stick figures. But for their next design,McAllister s group gave a leopard a three-dimensional aspect byputting parts of the drawing on two layers of the chip. The ani-mals outline went on the first metal layer; its spots on the con-tact layer (which is used to connect two metal layers vertically).

The innovative 3-D style elicited the desired oohs and aahsfrom colleagues, along with a bit of unwanted attention.

In the 1980s, when the design team had finished with achip, they would write the chip artwork patterns on to magnetictape and send it to the photomask shop, a momentous occa-

sion still known as tape release or tape out. The photomask

shop would then fabricate the dozen or m ore 40-cm 2 glassphotomasks containing each chip layer image.

Before the mask shop made the glass plates, techniciansimported the data from the m agnetic tape into a compu ter toview the chip m ask images. They looked for patterns causedby data-processing errors, by bugs in th e designer s outputsoftware, or by damage to the magnetic tape. They alsoscanned for design goofs such as crossed wires or missingconnections. A technician inspecting McAllister s masksoverlooked the leopard outline on the metal mask, butnoticed the cat s spots on a seemingly random part of thecontact mask and so mistook them for a flaw. She called

McAllister, who said , That s OK, those are leopard spots. We lost a day there.

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" GrouchoMarx brother makes his markon a Silicon Graphics chip.

" EnterpriseThis starship boldly goes where no art hasgone before, at least on this TI bipolar IC.

" The Little Engine That CouldFound chugging along on an Allen-Bradley/VLSI application-specific IC,this train is fabricated on two layersof metal and one of polysilicon.

" DilbertHe made it out of the funny

papers and onto a MIPS chip.

" The SundialIts located near the clock circuitry of the HP PA-7300 LC chip.

" Spaced Invader Apparently, East German chipdesigners also had some fun.

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In the process, HP managers were alerted to McAllister scartoon, but h is man ager just rolled his eyes and let it go.The lost day was irritating bu t probably insignificant, accord-ing to McAllister. He was not going to give me a dressingdown after all our effort. But this was one of a number of episodes th at eventually gave rise to the memo that requestedchip designers to just do chips please.

The cease-and-desist order to McAllister was far from unique.Chip graffiti eluded surveillance because it flew under the radarof both upper management and the relatively primitive com-puter-aided design tools of the early 1980s. Sophisticated designrules check (DRC) software would be developed only later thatdecade and perfected in the early 1990s. Until then, designershad to manually check the mask designs for errors, spendinghours hunched over giant paper plots of the chips. After muchediting, the error rate would sink to zero, at which point the tapewas released. Even with all that meticulous eyeballing, someerrors got through and so did a lot of graffiti.

As for man agemen t s attitude toward chip art, many tol-erated at least some graffiti because of the skill and status

of chip designers. They re hard to find, Davidson said.And if the designers want to do that stuff, the compan y can t

just fire them wholesale. Other companies were, and still are, less indulgent.

Davidson has found only two scraps of art on chips fromIntel Corp., and the company would not sanction an inter-view with the engineer responsible for them. For a U.S.chip-maker, Intel is un usual , but its attitude is apparentlyshared by its Japanese counterparts. Neither Davidson northe engineers at Chipworks have found a single piece of graffiti on a Japanese-made chip.

European designers, in contrast, seem quite fond of chipart. Graffiti graces devices from both Siemens (now Infi-neon) and SGS Thompson (now STMicroelectronics) thatare now displayed in the Silicon Zoo. According to Chip-works Elvidge, Siemens seems particularly tolerant, with

many chips featuring several versions of the same muscle-man [see photo, p. 51].

Tools erase graffitiManagement s disapproval is not the only foe faced by chip artat many companies. People aren t doing this as much thesedays for a couple of reasons, explained McAllister. One is that[the evolution of] large design teams spread out the spiritualownership of the chip among m any people, so there was lessmotivation for the individual artists. The other is we were doingchips that represented important product lines. Over time, wemade some mistakes with the little cartoons. Delaying one of these chips might cost a week, and a week became extraordi-narily valuable as the criticality of these chips went up .

Nor have shorter design cycles helped. Engineers don t havethe free time to get artistic, said Bob Weppler, now a senior proj-ect engineer at Rockwell Automation, Mayfield Heights, Ohio.

Weppler himself has had a hand in several graffiti-filledchips. At Allen-Bradley in 1988, he worked on a node adapter ICwith Michael Philippi and others then at Rockwell Semicon-ductor. The chip features references to Douglas Adams s novel

The Hitchhikers Guide to the Galaxy , including the answer to life,the universe, and everything (the num ber 42); a cricket wicket;and a sperm whale. Now, said Weppler, management s attitudeis: If you ve got time to design a sperm whale, why aren t you off designing something we can sell? [see photo, top left, p. 55].

The threat of a fatal design error spu rred the development of software tools that could automatically interpret drawings of ICsand search them for errors. DRCs started out as simple checksof chip wiring geometry, such as line width and line spacing. Asworkstation computers caught up in performance, the softwareevolved to check for wiring errors, like shorts and open s, by com-paring computer-aided design (CAD) layouts against functional

schematics of the chip, in the process known as functional check-ing. At this point, error-checking software started to discover

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A cheetah on a memory controller chip [above] was put there by former Hewlett-Packard chip designer Willy McAllister. It was digitized from a drawing, madeby his wife Monica, of a cheetahs photo on the cover of the September 1986 IEEE Computer magazine [right].

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flourishes like McAllister s leopard spots and one of Philippi sdesigns, an ill-fated bowl of petunias. It couldn t make it pastDRC and [Rockwell] had a policy that even artifacts had to passDRC, Weppler said.

Functional checking or layout-versus-schematic testingfinds a lot more graffiti, Scheffer confirmed. Even if the graf-fiti is DRC correct, it does not correspond to anything in theschematic, nor does it follow the u sual electrical rules of design.Its fairly easy to make graffiti that s DRC correct making itfunctionally correct as well is more work than most graffitiartists are willing to take on.

Another factor contributing to chip art s decreasing prevalenceis that today s designers are far more removed from the actualmask-manufacturing process than they were during chip graffiti sheyday. They have gone from the paper and pencil of the 1970s to

the stylus and electronic pad of the early 1980s to the polygon edi-tors (so-called because the features drawn were polygonal) of themid- to late 1980s. Until that point, graffiti artists could freely ply

their trade.Since then, the rule book has been rewritten. Now, chip

designers no longer have to plot out lines and spaces for thetransistors and interconnections making up each layer of achip. Standard design elements such as logic cells are sold byapplication-specific IC (ASIC) vendors and are integrated rightinto the chips Weppler now creates. Rockwell Autom ation nolonger has to bu y updated tools for him to create his own fea-tures, th ough he still has tools to automatically create text arti-facts, like the designers names or chip number.

Design elemen ts Weppler can t get off the shelf, he designsin r egister transfer level (RTL) language, which describes the

chips clock, data, reset inputs of registers, and the booleanlogic that goes between the register stages. These RTL designs

are captured in VHSIC (very high-speed IC) hardware designlanguage, or VHDL, where the designer defines the functionhe wants the chip to perform.

Instead of drawing flip-flops and logic gates by hand, hegets a synthesis tool to autom atically convert the equations anddefinitions that exist in VHDL into logic gates. The gates areautomatically placed and routed with another tool. Directhum an intervention is not needed. If we touch the layout atall, it is only to fix errors or add text artifacts like the partnumber or lists of designers names, said Weppler.

Managers like it that way. When companies lose moneybecause of this, they turn the screws down on it, said Johnson.When he became Transmeta s director of VLSI design, it fell tohim to set rules for embellishing Crusoe, the company s flagshipmicroprocessor, with graffiti . Having been a designer himself,

he could sympathize with the engineers desire for artisticlicense, but as a manager, he felt duty bound to be practical. Hecame up with a compromise solution: let the designers put

their initials and only their initials on the chip.That way all the people can say, Im there, my mark is on the

chip, and it s all much more carefully controlled, he explained.Despite his best efforts, though, a few outside contractors didmanage to carve unauthorized doodles onto Crusoe.

Whatever chip art is going on, it is don e the s ame way asstreet graffiti on the sly. Whether they use photolithographyor spray paint, tag IC interstices or subway cars, are thwartedby managers and high-tech manufacturing tools or hunted bycops, microchip designers an d graffiti writers are not easilydiscouraged from p racticing th eir craft.

For chip artists, figuring out how to skirt the automated

checkers is just part of the challenge. Said McAllister, If I didanother chip, I d figure out a way to get [a design] in there.

Mike Davidson, whose collection of chip graffiti appears on his Silicon Zoo Web site, starts the hunt for art by removing the protective cover on a packaged chip, here a Silicon Graphics MIPS R12000 microprocessor [actual size, far left]. At 500X magnification, strange artifacts are seen between a large cache and a series of buses. 2000X magnification reveals the SeminoleIndian logos of Florida State University.

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The Secret Art of Chip Graffitti