IEEE Spectrum December, 2007 - 43

54 IEEE Spectrum | December 2007 | NA

observed that the leakage currents in his device were usually
less than a nanoampere, or as little as 1 percent of those in
mesa transistors.
The nagging question on everyone's mind was, Can we manufacture these transistors in quantity? Initially, the planar process
yielded only a few working transistors in every 100-much worse
than the mesa process. But as various problems, such as pinholes in the oxide layer, were resolved, yields rose and doubts
evaporated. In April 1960, Fairchild sold its first planar transistor, the 2N1613-a metal cylinder about half a centimeter in
diameter and almost as high, with three little metal legs sticking
out beneath it.
A few months later, Noyce and Moore decreed that henceforth all the company's transistors would be planar. While
other semiconductor firms such as Rheem, Motorola, and Texas
Instruments had begun churning out competitively priced mesa
transistors, Fairchild boldly struck out in a promising new direction. Soon avionics manufacturers began to demand planar transistors because of their unmatched reliability. The Autonetics
division of North American Aviation, for example, insisted on
using Fairchild's planar transistors in the guidance and control
systems for the Minuteman missile.
Fairchild eventually licensed the planar process to other transistor makers-even Bell Labs and Western Electric. Either the
other firms followed Fairchild's lead or they exited the industry.

ELL BEfORE fAIRCHILD succeeded in commercializing Hoerni's device, Noyce had begun thinking
about what else the company could do with the
planar approach. In his 1975 interview, he credited patent attorney Ralls with challenging the
Fairchild team to consider other applications that could arise
from the new way of making transistors. Noyce realized that by
leaving the oxide layer in place, "the surface of the silicon then
had one of the best insulators known to man covering it." Which
meant that the electrical connections could be made by depositing strips of metal-such as the aluminum contacts Moore's
group had perfected-on top of the oxide layer. The strips would
be automatically insulated from the components underneath.

www.spectrum.ieee.org

lEFt: FAIrcHIlD SEMIcoNDuctor; rIgHt: StANForD uNIvErSIty ArcHIvES

recalled in a recent telephone interview. On 2 March, Hoerni
wrote another entry in his notebook titled "A method of manufacture of PNP transistors with oxide protected junctions." In
two more pages of text and drawings, he indicated specifically
how to fabricate such a device, though still stubbornly using
silver for the electrical contacts on the top side. By then, his
technicians were already transforming his novel ideas into actual
fabrication processes.
But all that progress came at a time of upheaval at Fairchild.
The same week that Hoerni was jotting down his fabrication ideas,
Edward Baldwin, who had been hired from Hughes Electronics
Corp. to serve as Fairchild's general manager, departed abruptly
to found Rheem Semiconductor in Mountain View, taking with
him five key people from the manufacturing division. After persistent urging by the other Fairchild cofounders, Noyce stepped
up to replace him, and Moore took over Noyce's position as
research director.
The following week, Hoerni invited several colleagues to
watch a demonstration of his new prototype transistor. Under
a microscope it appeared unlike any other Fairchild device. Less
than a millimeter across, it was completely flat-no mesa protruded in the middle. All that was visible was a circular metallic dot with a metal ring around it, plus the oxide surface layer
between them. It resembled a bull's-eye target with a portion
of it pulled out like a teardrop, making it easier to attach a wire
[see photos, "Silicon Flatland"].
What happened next is unclear. Some observers have claimed
that Hoerni suddenly spat on his transistor, to demonstrate that
such outrageous abuse had no ill effects on the oxide-protected
junctions. But Last and Moore don't recall him actually spitting, and Moore points out that saliva would have shorted out
the metal wires on the device. Even so, the demonstration was
dramatic and convincing, Last told me. "Gee, it's too bad Baldwin
had to leave last week," he recalls joking afterward.
Things moved swiftly after that. It was obvious that Hoerni's
creation was far more rugged and reliable than the mesas. And it
also proved to have much lower leakage currents-small, wrongway trickles that can seriously degrade transistor performance.
In a Fairchild report released the following year, Hoerni

http://www.spectrum.ieee.org

Table of Contents for the Digital Edition of IEEE Spectrum December, 2007