Strategy and tacticsfor integrated electronics

The rate of technological innovation has been increasing without long-term goals and strategies, can be dis-dramatically in recent years, and so has the risk that a astrous.given technology may become obsolete before innova- To make sound tactical choices, each enterprise musttion is complete. Thus, tactical choices must be made have a long-term view of its markets and resources.on the basis of long-term goals. Probably nowhere is These will determine the measures of cost, performance,this problem more complex than in the move toward and reliability for its innovations. But these classicalintegrated electronics. By way of example, this article measures are not enough to ensure economic survival.describes how the "adaptive strategy" approach has We must also ask about the potential longevity of abeen employed on a company-wide scale as a meansfor guiding the Bell System's choice of materials andprocesses for integration.

FIGURE 1. Growth of active-component technologies in theAt an ever-increasing rate over the past century, in- electronics industry.

formation-processing systems have grown in size, com-plexity, and versatility. Paced by previous innovations in 5000 - -;;-; -; - ;;;#+ ;; ;;0component technology, their change is being acceleratedby a newer one-that of integrated electronics.

In earlier eras, tactical choices for innovation were 2000.-simple to make. The number of potential markets and /technologies was limited. New developments tended tocomplement, rather than compete with, the older com- -1000-ponents; each was needed to build a complete systemcapability. Equally important, the time interval between 0

c' 50C0decisions was long- long enough to ensure a rewarding .oreturn on investment in innovation. E

In the past two decades, however, the number of g Alt tubestechnologies possible for innovation has been growing r 200 -rapidly. They are more competitive with each other andwith the old. And faster change increases the risk that a < i - -technology will become obsolete before innovation is Allintegratecomplete. Today there are more opportunities to lose eleotcyour shirt than to make a killing. Short-term tactics, 50

This article was presented originally as the keynote address at 1920 1930 1940 1950 1960 1970the Intcrnational Solid-State Circuits Conferetnce, Philadelphia.Pa., February 19- 21, 1969. Year

26 IEEE spectrum JUNE 1969

In today's rapidly chaniging market, any effectivetactical evaluation of a new technology should be based oi0 awell-conisidered aniswer to the question "Is it adaptable?"

Jack A. Morton Bell Telephone Laboralories, Inc.

technology. Can it survive the changes that are sure to standing to gauge the lifetime of old and new tech-come in knowledge and markets? Is it adaptive? This is nologies.the strategic question!To better understand this long-term property of The adaptability of component techniques

adaptability, let us review the past cycles of component The first era of electrical information systems dependedinnovation. Many of these technologies are still vigorous upon relays and telephones. Together with passive coim-today. Perhaps we can identify the essential elements ponents. they supplied the functions essential to beginof their adaptability. Hopefilly, we can use this under- telegraphy and telephony. But their electromechanical

nature set limits to the analog and digital ftnctionsthey could perform. and prevented the full developmentof communications.The second era grew from the innovation of tube

FIGURE 2. Electronics industry markets. technology. In communications. it provided long-dis-tance carrier transmission over wire. cable. and radio.

5s =I Even though tubes could perform digital functionisfaster than relays, they did not replace them. Their cost

-- i :I A and reliability limitations prevented this. More tele-*o _ . _ .phones and relay switching systems were required for

the communications markets expanded by electronicV transmission.

-2 lo X > e:. 0 : r XA;: S tSimultaineously, tube technology created new markets0 -OD <2 X 0 6 4t :tXX > rOr electrical analog systenms. Broadcast radio and home

recording spawned a vigorous new consumer market.o _0 ig :, a, B$'llu"':00t;;;,0:00p,'.'10X'Over some 40 years, electron tubes were greatly improved

'and new types again complemented the old. The analogfunctions of tubes were extended and new electrooptic

s2 gj ^; i ........................8tt':.functionswere added. Until the transistor era, however,new component innovations did not displace the older

<2 l b tS0.>110HW-Wtechnologies--they supplemented them. As each com-

A S S 4 X 4 i ponent innovation was added. system capability grew.~~~ I ~~~~~Following World Wair 11, television stimuLlated the con-

0.5 sumer mrket, militairy maisrkets grew rAspidlyand tube~~~ I ~~~~~~comiputers opened a new induistrial market. As a reSuilt,

/ ~~~~~~~~relayand passive comiponents have had growth cuirvesX Xalmnost identical to that shown for tuLbes in Fig. . Because

1920 1930 1940 1950 1960 1970 of the slow pace of change and the complementaryYear nature of component technologies during the first two

Mortoi- Strategy andl tactics for intiegraited clectronlics 27

eras, the return on their innovation continued for long which had to be terminated, protected, and assembledperiods. one at a time.But these apparent virtues posed serious problems for Many of us could see these limitations in the late

further system growth. Each component technology 1950s; in fact, the opportunities for breaking throughwas highly specialized. Each relied on widely different them appeared with the introduction of batch diffusionphysical phenomena, material systems, and processes of itself. In 1956, at Bell Telephone Laboratories, Ross de-manufacture. As a result, they differed in their intrinsic veloped an integrated silicon binary counter using planarlimits of size, power, and speed; they also differed in their p-n-p-n structures. In 1958, at Texas Instruments, Kilbycost and reliability. Their limitations and differences be- developed the first silicon circuits containing mesacame high economic barriers to increasing system size diodes, transistors, and resistors interconnected withand complexity. wire leads. A little later at Fairchild, Noyce and his

Indeed, it was these problems that led to the invention co-workers introduced the batch interconnection ofof transistors. Their innovation has given us a versatile planar elements in a silicon chip through the use ofcomponent technology that combines the electronic speed evaporated wiring.of tubes with the low cost and high reliability of relays. Thus, by making all the elements and intraconnectionsIn just 20 years, semiconductor technology has improved of a circuit at one time, and by making many such cir-by several factors of ten in performance, cost, and cuits in a slice, the individual termination-capsulationreliability for both analog and digital functions. As shown operations were moved from the element to the circuitin Fig. 2, all electronic markets have been further stimu- level. Planar silicon circuits gave us large improvementslated. Since the early 1950s, the military and industrial in cost and reliability. For digital functions, they excelledmarkets have grown at a faster rate than the consumer in performance as well.market. This has resulted in a corresponding growth As a result, planar circuits have been applied rapidlyrate for semiconductor components that is almost three to digital systems. They constitute the lion's share oftimes the rate for tubes; see Fig. 1. industry's total effort on integrated electronics. As shown

Let us reexamine the major semiconductor innova- in Fig. 1, annual sales of all kinds of integrated com-tions, but now from the viewpoint of their adaptability. ponents have been growing at the same rapid pace as didThe physical phenomena of semiconductor components discrete semiconductors. The steep slope and small timeare themselves highly adaptable. They have proved their displacement of these curves illustrate the new pace ofversatility for a wide range of electrical analog and digital innovation and the difficulty of getting an adequatefunctions. Today semiconductors can provide electro- return on innovation.acoustic and electrooptic functions as well. Most of ourinnovations have had to be in the materials and processes The need for anneeded to achieve realization of their intrinsic physical integration technology that is adaptivecapabilities. Today's situation is reminiscent of the mid-1950s,

Point-contact technology was limited in all three when alloy transistors were riding high, but we weremeasures of effectiveness; it was difficult to understand looking ahead to the batch technology of diffusion. Nowand had a very short life. Grown-junction technology we see the "one-at-a-time" economic barriers at thewas the first stimulant to market development. Because intercircuit rather than at the interelement level.we could apply science to development, we were able One response is, "If some silicon integration is good,to extend the frequency, power, and reliability of both let's have a lot." Large-scale integration (LSI) impliesgermanium and silicon devices. Nevertheless, it too had putting the maximum amount of a system on the largesta short life. Lower-cost alloy technology took over in slice. The individual terminations and cans are moved toconsumer ratio, and its superior switching devices paid the highest possible system level. However, this approachoff in computers. By the late 1950s, alloy germanium results in low yields; a maximum level of integrationtransistors had about reached the limitations of their implies a minimum production run. Different systemstechnology. By 1955, the high-precision, batch processes designers ofttimes cannot, and many times will not, useof oxide masking and diffusion had been demonstrated the same LSI design. Costs never come very far downfor silicon as well as germanium. So, again, a materials the learning curve. Furthermore, the development of LSItechnology did not last very long. In just a few years, requires maximum cooperation and risk-taking betweendiffusion surpassed alloy technology in all performance component and system specialists; and this is reallyand economic measures. Equally important, it was a tough problem of integration.adaptive to different materials, device structures, and To alleviate such problems, some innovators proposemarkets. With the easy addition of epitaxial and planar a standardized-slice approach to LSI. Each silicon slicetechniques, diffused silicon technology proved its adapt- contains a standardized array of circuits in quantitiesability to new knowledge, and new functions and markets greater than required and therefore becomes useful togrew again. more systems. This results in more profit from the

Thus, until the introduction of batch diffusion, the learning curve and reduces the amount of interactioninnovative life for transistor technology was short. The needed between component and system designer.saving grace came from industry's rapid application of Nevertheless, in all these approaches to LSI, "discre-each advance and the resulting growth of both old and tionary wiring" is essential to complete the slice integra-new markets. In just a few years batch diffusion was able tion. In all cases, we start more circuits on the slice thanto push discrete transistors to their limits, required. Discretionary wiring then measures all circuits

But, as we know, these limitations of planar transistors and stores the locations of good ones in computerwere not due to the physics nor to batch diffusion. They memory. A unique set of wiring masks must then bewere limitations of the technology for discrete elements, made for each slice. Finally, each different slice is intra-

28 IEEE spectrum JUNE 1969

connected, terminated, and capsulated-hopefully at believe that planar LSI is not amenable to total batchhigh yield. Let us see if there are problems in these fabrication, and it is not adaptive to different systemsapproaches. or new phenomena.

1. Each silicon slice uses some of its area for bad At different levels in different systems, all systems be-circuits. This limits the complexity of an array and come hybrid. They must contain interconnected materialreduces speed because of unpredictable wiring parasitics. subsystems, alike or different, for economic or per-

2. The test information of each slice and the design, formance reasons. We have come full circle on thefabrication, and application of each wiring mask repre- upward spiral of innovation -from the thesis of mono-sent costly software and hardware-all different for each lithic integration to the antithesis of system partitioningslice. into specialized, but integrated, subsystems.

3. The need for one-at-a-time complex wiring patternsplaces severe demands on high-yield intraconnection Maue faatblt n nerblttechnology. It also can degrade the yield of the uinder- Today's innovator of electronic systems, therefore,lying circuits. faces major new tactical choices. What strategy of par-nEach pLnar array is terminated with individual titioning and integration should guide him? How shouldwie leach panararrotec sterminatedwith aicomplexcanhe partition his total system between subsystems ofwire leads and protected with a complex can.

which material, and how should he interconnect them?A serious drawback to discretionary wiring is its in- He knows that his requirements will depend on his

crease of one-at-a-time operations-its loss of batch markets and how they change. He knows that his presentfabrication at a late, costly point in the process. Remem- materials technologies will change with time; and heber, it is batch fabrication of identical planar chips that knows that research will lead to new materials andhas brought us our large gains. It was the cost of in- ftnctions. Can he select a technology for integrationdividual operations required on planar elements that that can use such change without becoming obsoleteled us to integration. And remember that batch fabrica- before he gets his bait back? What properties shouldtion can pay olF only if there is enough production to materials subsystems have to provide simultaneouslybenefit from the learning process. Even in a system whose the benefits of integration and adaptability? To somefunctions can be supplied by a common silicon slice, the extent, these properties appear to be in conflict. To makeneed for good yield requires partitioning between iden- tradeoffs between them, we must understand the essencetical silicon subsystems. of each.

Equally important, however, is the fact that any single The essence of integration is total batch fabrication ofmaterial is always limited in the variety of ftnctions it each material subsystem and the hybrid system- -dividingcan perform well. Silicon does not provide the highly the cumulative cost of many process steps by the largeprecise, stable resistors and capacitors needed for many number of elements and subsystems processed per batch.analog functions. It is difficult to intermix bipolar and We, of course, always want to minimize the number ofunipolar elements in the same slice. Furthermore, new subsystems and the number of process steps in each.physical phenomena in dilTerent material systems are But most important, we need batch fabrication of alland will be forthcoming. We will want to integrate them process steps, ranging from element formation, isolation,with the functions that silicon does well. In short, I and protection to intraconnection and termination of

FIGURE 3. Two complementary, compatible silicon chips.

Morton- Strategy and tactics for integratedi electronics 29

FIGURE 4. Silicon chip, showing beam leads. FIGURE 5. Batch-fabricated beam crossovers.

each subsystem. In addition, we need batch assembly and fabricate Lunipolatr and bipolar transistors and diodes;intraconnection of the hybrid system. The hybrid yield photoelectric and electroluminescent devices; domain,should average, not multiply, the yields of each subsystem. avalanche, and lasing devices; discrete and distributedHybrid intraconnection should combine only good resistors; and capacitors. We also have a number of'subsystems, without damage. choices for the essential integrating processes of elementThe essence of adaptability is technical and economic isolation and protection and subsystem intraconnection

flexibility in partitioning a total system into its similar and termination. We are blessed, or cursed, with aand different subsystems. To benefit from batch fabrica- technological feast, which can jade our judgment.tion, we Muist have sufficient cumulative produiction of To choose from among these possibilities, each of useach to permit operation well down on the learning-cost must have a clear idea of the long-termi objectives forcurves. For easy tradeoffs between subsystem costs and innovation: what kind of systems for what markets;hybrid assembly costs, we must have complementarity what business we want to be in. From such a viewpointand compatibility between materials subsystems. Thus, each of' us can develop a long-term strategy. Besides thesubsystems must be well-matched at their interface in appropriate measures of performance, cost, and reli-size, topology, and metallurgy-and they should be ability, ouir strategy must include the essential measures

comparable in cost and reliability. If such requirements of integrability and adaptability.are met, the designer can partition his system optically By way of example, let me show how the objectives of'with regard to both performance and cost. He also will the Bell System and an adaptive strategy have guidedbe able to change his partitioning as yields of old tech- our choices of' materials and processes for integration.nologies improve, as new materials and phenomena Over the years, we have evolved a deceptively simpleappear, and as markets and systems requirements con- objective: "To provide the best communications servicetinue to change. at the lowest cost consistent with financial health."

However, w-hat was the best yesterday is not best today-Choosing an and the best today will not be the best tomorrow. Toadaptive technology for integration meet this goal always, we must have continuing innova-

I shall not attempt to describe all of the electronic tion. But the nature of the business demands that all thematerials, structures, and processes now available for parts, old and new, of our network must work compatiblyinnovation. To name just a few, we have bulk semicon- and continuously. Both for service and financial health,ductors such as silicon, germanium, gallium arsenide, and this complex network cannot be scrapped and rebuiltgallium phosphide; to varying degrees, these materials in whole, or in large part, every few years. It must operateare well understood. In addition, we have thin and continuously while it is being maintained and trans-thick films of a variety of conductors, insulators, and even formed. "Innovation in such a system is like getting aa few semiconductors, and some of these are well under- heart transplant while running a 4-minutte mile!"stood. We have a variety of processes for altering the Nationwide communications also requires a wideelectronic struiCture and topology of these materials, variety of electrical functions. All the digital functionsTechniques such as oxide masking, photolithography, of logic, memory, switching, and pulse code transmissionepitaxy, diffusion, alloying, sputtering, evaporation, and are required. Speeds range from a few pulses per secondion implantation are all usefuil. With them, we can batch to greater than 500 megabits per second. Memory re-

30 IrrE spectrum JUNE 1969

FIGURE 6. Sampling of thin-film tantalum circuits.

quirements cover the full gamut, with access times rang- fabrication to the highest system level become essentialing from milliseconds to nanoseconds, and capacities criteria for oir innovations.from kilobits to hundreds of megabits. In the analog But the size and diversity of the Bell System, the needfield, we need all known functions-modulators, de- for compatibility of its parts, and the demand for con-modulators, filters, oscillators, amplifiers, and access tinuity of its service make for long innovation intervals.transducers, over the full spectrum from kilohertz to These characteristics and the corresponding high cost ofhundreds of gigahertz. Amplifier bandwidth is never innovation dicate that our switched network, and itsgreat enough; noise figures and distortion are never low technology, must be highly adaptive. For all these reasons,enough. The only performance dimension we do not we have chosen a more complex hybrid approach tocover is that of power, although we need ranges from integrated electronics. We believe it has the adaptabilitymicrowatts to watts. In short, our requirements for per- to meet our wide variety of changing requirements forformance cover most of those encompassed by all other integrated electronics.markets. Currently, it is composed of two diflerent, but comple-

Finally, the marketing of service, rather than product, mentary and compatible, materials systems: One is basedrequires a dillicult balance between performance, cost, on the electronic frunctions available in bulk silicon;aind reliability, for each of the dilferent functions and the other depends on the electronic ftnctions of thin-filmenvironments met in transmission, switching, and cus- tantalum and its compounds.tomer systems. Service is measured by the kind and As in planar silicon, our beam-lead sealed-junctionamount of performance per annual dollar of expense. technology uses oxide masking, photolithography, andAnnual expense includes mtnufacturing cost, installa- diffusion to define the structure of bipolar or unipolartion cost, and maintenance expense of systems, and the elements. But it uses a more complex metal -insulatoranmortized cost of land and buildings. As systems increase system to achieve batch fabrication of element ohmicin complexity and labor costs rise, assembly, wiring, contacts and in sitt protection as well as subsystem intra-installation, and maintenance become increasing frac- connections, crossovers, and beam-lead terminations.tions of our annual expense. Reliability and batch Because of the nature of the beam-lead structuire, air

Morton Straitegy iilr tactics for intcgraltcdl clectroniics 31

are illustrated in Fig. 5.The color block on the left SUIMS Up the properties

and capabilities of today's beamil-lead sealed-junctiontechnology'.The thin-filmi subsystemi that comiplemients the silicon

technology statrts with thin filmis of sputtered tantalumn of'-.-. controlled chemical and physical strUCtuire. By alitering

filmi strUCtuire, we cain design for a wide ratnge of resis-tivities and temperatLure coefficients for discrete or dis-

X lt~ni~1 . !tributed resistors. Using the same mask-making progratiisand machines as for silicon, We Llse photolithography todefine the topology of resistors, capacitors, and intrt-

*~~~fency~~~~~~~~~onnections.XS . ! 7!Batch anodization of the tantalumn filiml permits trim-

l l F l l nming of resistors to high precision and adlustnient of.................... the capacitance and breakdown voltage of capacitors.

*4 l 0 00 0 0 In addition, anodization provides contaminant protec-tion for the resistive films. Finally, we use the samestrutigure and processes as in silicon to fori beam cross-

X.~.. overs in the tantalum film circuits.We believe we can achieve comtplexities for tantalumiers

integrated cirCuitS commenssrate with any other knownsystems. bUt with higher levels of precision, stability, andreliability. We alsohaove the option of making distributed

tpassive networks. Figure 6 illuastrates a few of the varietyof thin-film circuitS possible with this technology. One

isolation as well as junction .isolation.ofelementsis of the most demanding is a pair of twin-T RC filters ofhigh precision and stability. Together with a beam-leadsilicon chip containing two 5-stage, stabilized amplifiers.this circuit provides precision and stable tones for Touch-Tone signaling. At the bottom is shown a digital-to-analogdecoder developed for our high-speed pUlse-code-modula-otin system. This nine-bit decoder operates at speedsof 108 megabits per second. The resistor ratios of thisnetwork Muist miaintain a precision and stability of

_ ~~~~~~~~0.025percent for 20 years.Like the silicon integration system, as Outlined in the

color block on this page. thin-filr metal -insulatortechnology also provides batch fabricaition of all neededoperations for passive circuits and interconnection of

isyolation is well tejulnction isola tion of elements i these and silicon chips. The tantalum system has thepossible. same range of performance and reliability as those ob-

Detailed descriptions of the materials, structures, and taied from the complemientry silicon system.processes of this technology have been given elsewhere The adaptability of hybrid technology to some of theand will not be repeated here. Instead, let me sum our functions needed for the Bell System is shown in Fig. 7.experience by saying that we can achieve complexity In each case, the partitioning between silicon chips andlevels for bipolar and Lnipolar subsystems coi menSirate between silicon and thin-fil ournits is determined by thewith planar technology. It is true that the nunber offsnctional requirements and the current economics ofbatch process steps is larger than for a raw plaenar chip, the two materials technologies. For example, the 1024-but there are no costly, one-at-a-time, termhination- bit memory module contains 32 bipolarstordage cells ofcapsulation processes required to complete the sub- 32 bits each and 12 bipolar access circuits. As bipolarsysteni. Moreover, the early in siiw protection of the yields improve, we can increase the number of bits persilicon Sirface imisproves yields and gives higher reli- chip; we can even shift easily to a competitive 1Gicrability. Figure 3 shows a pair of complemientary. com- storage technology, if desired.patible silicon chips. At the left is an iGHndrmemory chip In the middle is shown a switching network containingcontaining 128 bits and 768 elements. On the right is en32 bipolar chips. Each chip contains four istnds Of fouirassociated bipolear access chip containing 344 diodes. p-n-p-n crosspoints each, and oulr islands of four accesstransistors, and resistors. Although the chipS use systems diodes each. The islands are air-isolated to meet stringentof difrerent materials to optimize performatnce and crosstailk requiirements. Thus, the hybrid network con-reliability, they are comipatible for hybrid battch assemnbly tains 512 crosspoints, with 512 associated access diodes.on thin-filmi substrates. Figure 4 shows how beami leads Next, to the right, is the analog Touch-Tone hybridcan provide air isolation within a silicon chip. Latrge mentioned previously and on the extreme right is a micro-reduictions in interelem-ent parasitics and a modest wave amplifier module using thin-film distributed passivereduiCtion in process steps resuilt. The featLures of batch- elements and two beam--lead transistors with high gain -

faibricated beamn crossovers in schemaiztic and aCtuial formi bandwidth. It has a modular power gain of 15 dlB

32 iiii. spectrumn JUNi 1969

FIGURE 7. Functions realizable by silicon and tantalum technology.

from 10 MHz to 2 GHz, flat to 11.5 dB. As our tech- "RSI." the righJ scale of intlegraiion for each of our manynology improves, we expect to integrate several stages as a ditlerent systems. We believe that RSI is an adaptivecomplete amplifier. technology- that it can survive and be renewed for many

years to come as our present technologies improve, as ourConclusions system needs change, and as new materials functions areTo sum up, both material subsystemiis tise batch fabrica- added.

tion for all process steps up to their interface. Since theyalso match at their interface in topology and metallurgy,they are compatible as well as complementary in func- Jack A. Morton (F) is vice president in charge of electroniction. They can be batch-interconnected to form hybrid components at Bell Telephone Laboratories, Inc., Murraysystems for the high reliability and wide range of analog Hill, N.J. He received the B.S. degree in electrical engineer-aind digital performance required. They share several ing from Wayne University in 1935 and the M.S. degree inbasic processes in common, and they share some ma- engineering from theo Unirinty936 and continued part-timeterials and structures. Thus. we benefit from common postgraduate studies in physics at Columbia University un-process innovations. They are comparable in cost and til 1941. During the early part of his career he did researchreliability, and further development is aimed at bringing work on coaxial cable repreaters and microwave amplifiers.theni still closer together in size. Finally, they are in- DuringWorld Warli heconcentratedonthedevelopmentof

microwave electron tubes and radar receivers. After the wardependently batch-fabricated and tested before batch he designed the microwave tube that is the heart of theinterconnection, and the bonding process has negligible transcontinental radio relay system fortelephoneand televi-efTect on their quality. As a result, hybrid yields are the sion transmission. In 1948 he took charge of the company'saverage, not the product, of subsystem yields. first development work on semiconductor devices. Later

Thus, there is a flexible choice between how much he became responsible for applied research and develop-ment of electron tubes, solid-state devices, and electro-

function is embodied in each silicon and tantalumii sub- mechanical and passive devices. He was elected to hissystem. Tradeoffs between cost and performance can be present post in 1958. Mr. Morton has been awardedmade easily. The interface between the two materials honorary D.Sc. degrees bycan shift flexibly for difTerent systems, and with the Ohio State and Wayne Univer-improvements that are coming in each materials tech- sities. He is the recipient of a

nology. For new electronic functions, such as thoseb

the IEEE David Sarnoff Awardaivailable from avalanche, domain, laser, and electro- and the IEEE Reliability Groupluminescence phenomena, new materials are required. X Award, received in 1965 andBy extending beam-lead sealed-junction principles to 1969, respectively. Membershipsthese difTerent semiconductors, they can become syner- ainclude Phi Beta KPi,sigmagistic parts of our present technology. Xi, and The National AcademyWe believe this approaich to integration can provide 0of Engineering.

Morton --Strategy and tactics for integratedl elcctronics