Classic Patents/US 3,138,743

Mid-Century Electronic, Nuclear & Materials Revolution (1920–1990)Microchips, Solid Circuits & Semiconductor Integration

Jack Kilby Monolithic Integrated Circuit

US 3,138,743

Single-Crystal Semiconductor Substrate Integrating Transistors, Bulk Resistors, and P-N Junction Capacitors

Inventor(s)Jack S. Kilby

Grant Date1964-06-23

Filing Date1959-02-06

LocationDallas, Texas

Jack Kilby's historic 1964 master patent for Miniaturized Electronic Circuits—the foundational Texas Instruments breakthrough that invented the Monolithic Integrated Circuit (Microchip). Created during the famous 'monolithic idea' summer of 1958 at TI, Kilby realized that if all circuit components—active transistors and diodes, passive bulk resistors, and p-n junction capacitors—were fabricated entirely out of a single piece of semiconductor material (germanium or silicon), the 'Tyranny of Numbers' (interconnection failure) would be broken forever. Kilby demonstrated the first working monolithic integrated circuit (a phase-shift oscillator on a sliver of germanium) on September 12, 1958, sparking the microelectronics revolution that powers every computer, smartphone, and spacecraft on Earth.

USPTO PDF

Engineering Analysis & Physical Principles

How It Works: Step-by-Step Mechanical & Physical Breakdown

In the late 1950s, the electronics industry ran into a catastrophic roadblock known as the 'Tyranny of Numbers.' While discrete transistors had replaced bulky vacuum tubes, complex computers and military guidance systems required hundreds of thousands of individual components—each with two or three hand-soldered wire leads. With so many soldered joints, statistically, systems failed almost immediately after being turned on. In the hot summer of 1958 at Texas Instruments in Dallas, Jack Kilby was a newly hired engineer who had not yet accrued vacation time. Left alone in the laboratory while senior staff were away, Kilby asked a profound question: If Texas Instruments is a semiconductor company that knows how to manipulate silicon and germanium, why use other materials at all? Kilby realized that resistors could be carved out of semiconductor bulk material, capacitors could be made from reverse-biased p-n junctions, and transistors could be built on the same piece. On September 12, 1958, Kilby demonstrated the first working monolithic integrated circuit in human history—a phase-shift oscillator on a sliver of germanium about the size of a postage stamp.

The Core Breakthrough Mechanism

Kilby's Monolithic Integrated Circuit operates by co-fabricating all circuit organs within a single continuous crystal wafer: (1) Bulk Semiconductor Resistors: Electric current flowing through a shaped channel of doped semiconductor encounters bulk resistance governed by Ohm's law and resistivity ( $R = ho L / A = R_{ ext{sheet}} cdot L / W$ ). By etching narrow serpentine mesas, precise resistor values from $100;Omega$ to $100; ext{k}Omega$ are formed directly in the silicon/germanium bar without discrete resistors. (2) P-N Junction Capacitors: When a p-n junction is reverse-biased, mobile charge carriers are pulled away from the interface, leaving an insulating depletion zone of width Mathematical notation unavailable. This depletion layer acts as a dielectric between the conductive p and n regions, creating an integrated voltage-variable capacitor (Mathematical notation unavailable). (3) Mesa Bipolar Transistors: By sequentially diffusing acceptor (p) and donor (n) impurities into the substrate and etching mesa plateaus, active NPN or PNP transistors with high current gain (Mathematical notation unavailable) are formed right alongside the passive resistors and capacitors. (4) Interconnection: Kilby used fine gold flying wires bonded via thermal compression to connect the mesa tops into a functioning flip-flop or oscillator circuit.

Interactive Real-Time Physical Simulation

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INITIALIZING THREE.JS WEBGL SIMULATION...

Host-Model Telemetry/Computed Readout

Monolithic Integrated Circuit Solid-State Electronics

Collector Load Resistor

6402Ω[ML²/I²T³]

P-N Junction Capacitance

0.23pF[1]

Collector Current

0.91mA[I]

Propagation Delay

6.63ns[T]

Phase-Shift Osc. Frequency

44126.7kHz[1/T]

Packing Density

135.8M parts/ft³[1]

Supply Voltage (+Vcc)6 V

Resistor Path Length500 µm

Resistor Path Width50 µm

Capacitor Reverse Bias3 V

BJT Base Drive Current40 µA

Detailed Component Architecture

1Monolithic Semiconductor Substrate

A single continuous wafer of single-crystal germanium or silicon acting as common structural host and collector.

High-purity crystalline semiconductor with controlled donor doping ( $N_d approx 10^{15} ext{ cm}^{-3}$ ) providing carrier mobility $mu_n approx 3800 ext{ cm}^2/ ext{V}cdot ext{s}$ (Ge) or $1400 ext{ cm}^2/ ext{V}cdot ext{s}$ (Si).

19th-C. Term: Wafer or bar of single-crystal semiconductor materialModern: Monolithic semiconductor substrate / Silicon wafer

2Integrated Bulk Semiconductor Resistor

Narrow shaped mesa path of semiconductor material providing defined linear resistance between ohmic contacts.

Resistance Mathematical notation unavailable, where sheet resistance Mathematical notation unavailable. Length-to-width aspect ratio determines total resistance.

19th-C. Term: Elongated resistor region / bulk semiconductor pathModern: Diffused / Well Semiconductor Resistor

3Integrated P-N Junction Capacitor

Reverse-biased semiconductor junction utilizing depletion zone width as dielectric layer.

Transition junction capacitance Mathematical notation unavailable, providing voltage-controlled AC signal coupling and filtering.

19th-C. Term: Capacitor defined by a p-n junction / reverse-biased junctionModern: Junction Varactor / MOS Capacitor

4Mesa Diffused Bipolar Transistor

Active three-layer (collector-base-emitter) switching and amplifying element isolated by mesa chemical etching.

Vapor-diffused base layer ( $t_b approx 1.5;mu ext{m}$ ) and alloyed emitter dot delivering current gain $alpha = 0.985$ , Mathematical notation unavailable, with collector cutoff frequency $f_T > 25 ext{ MHz}$ .

19th-C. Term: Mesa transistor / thin layers of opposite conductivity typesModern: Integrated Bipolar Junction Transistor (BJT)

5Thermal Compression Wire Bond Interconnects

Gold flying wires bonded with heat and pressure to bridge isolated component mesas into functional circuits.

Fine gold wire ( $D approx 25;mu ext{m}$ ) thermo-compression bonded at $300^circ ext{C}$ directly to alloyed ohmic gold-germanium contact pads.

19th-C. Term: Conductor means / gold bonding wires / flying leadsModern: Wire Bonding / Planar Metal Interconnects

Engineering Principles & Equations

Governing Equations & Engineering Principles

Authored explanation paired with its stated mathematical relation

Semiconductor Bulk Sheet Resistance & Geometric Scaling

Solid-State Physics & Integrated Circuit Design

Mathematical Governing Law

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Terms:

Plain English DecoderHover or tap any highlighted phrase

The total equals multiplied by over , derived from and .

R

Integrated Bulk Resistance

Total electrical resistance of the shaped semiconductor path (Ω).

ΩM L^2 T^-3 I^-2

Determines the collector load and base bias resistances in the monolithic solid circuit.

Live Physical Value:

6402 Ω

Physical Principle & Engineering Insight

Bulk semiconductor resistance depends linearly on the aspect ratio L/W, allowing precise resistor values to be shaped directly into the semiconductor crystal substrate without discrete resistors.

P-N Junction Depletion Transition Capacitance

Semiconductor Device Physics

Mathematical Governing Law

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Terms:

Plain English DecoderHover or tap any highlighted phrase

The across depends on , , and , scaling inversely with plus and .

C_j

P-N Junction Transition Capacitance

Dynamic small-signal capacitance of the reverse-biased junction (pF).

pFM^-1 L^-2 T^4 I^2

Acts as an integrated capacitor for AC coupling and filter networks.

Live Physical Value:

0.23 pF

Physical Principle & Engineering Insight

Reverse-biased p-n junctions create an insulating charge-depleted layer that acts as a dielectric, providing integrated microchip capacitors whose value is dynamically tunable by applied voltage.

Semiconductor Bulk Sheet Resistance & Geometric ScalingAuthored Principle 1

Stated relationMathematical notation unavailable

Governs the resistance of integrated semiconductor paths. By controlling dopant concentration and mesa aspect ratio, precise resistor networks are created directly inside the crystal.

P-N Junction Depletion Transition CapacitanceAuthored Principle 2

Stated relationMathematical notation unavailable

Reverse-biased p-n junctions act as parallel-plate capacitors whose dielectric thickness expands with applied reverse voltage, enabling integrated coupling capacitors.

BJT Current Amplification & Monolithic RC Circuit DynamicsAuthored Principle 3

Stated relationMathematical notation unavailable

Bipolar transistor current amplification combined with integrated RC feedback networks produces self-sustained oscillations and bistable flip-flop digital switching inside a single monolithic bar.

Interactive Schematic Sheet (Figure 1)

Perspective cross-section of semiconductor wafer showing bulk resistor formed by shaped semiconductor path and capacitor formed by reverse-biased p-n junction.

1.00x

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Why It Still Matters

Jack Kilby's invention of the monolithic integrated circuit is the foundational spark of the Digital Age. Today, billions of integrated circuits containing up to 100 billion transistors on a single silicon chip (such as Apple M-series, NVIDIA AI GPUs, and Intel Core processors) power all global computing, smartphones, artificial intelligence, cloud servers, medical equipment, automotive engine controls, and space exploration.

Legal Claims Decoder (25 Numbered Claims)

Compare dense legalistic claims directly with decoded plain-English functional specifications.

Claim #1Independent Master Claim

1/25

Verbatim Historical Legal Text

“1. In an integrated circuit having a plurality of electrical circuit components: a wafer of single-crystal semiconductor material containing a plurality of active and passive circuit components, said active circuit components each including at least two thin layers of semiconductor material of opposite conductivity-types extending to one major face of the wafer with p-n junctions extending to said one major face, said passive circuit components each including at least one discrete region of the semiconductor material spaced on said one major face away from the thin layers of said active components, and conductor means for interconnecting said components into an operative circuit.”

Plain English Engineering Translation

The master patent claim for the integrated circuit: a single-crystal semiconductor wafer containing multiple active components (with p-n junctions extending to the surface) and passive components (in discrete spaced regions), interconnected by conductors into a functional circuit.

Key Protected Innovations:

Monolithic single-crystal integration of active and passive componentsCo-planar surface termination of p-n junctionsInterconnected complete functional electronic circuit

Historical Legal Impact:

The broad foundational patent claim establishing legal priority for all monolithic integrated circuits.

The Historical Bottleneck

By 1958, complex electronic computers required tens of thousands of discrete transistors, diodes, resistors, and capacitors. Hand-soldering millions of individual wire joints created the 'Tyranny of Numbers'—a barrier where systems became too large, expensive, and unreliable to function.

Why Prior Art Failed

•Every component was packaged in a separate metal can or ceramic tube
•Interconnections required manual wire routing and soldering across circuit boards
•Solder joint failure rates scaled exponentially with system component count

The Breakthrough Insight

“All electronic circuit functions can be created out of a single semiconductor material: bulk resistance for resistors, p-n junction depletion zones for capacitors, and diffused layers for transistors, allowing an entire computer circuit to be fabricated on a single monolithic bar of silicon or germanium.”

Patent Wars & Legal Litigations

Vs. Robert N. Noyce & Fairchild SemiconductorInfringement Challenge

Rival Claim & Defense:

Planar process with silicon dioxide passivation and evaporated aluminum interconnects

Litigation Conflict:

In January 1959, Robert Noyce at Fairchild conceived the planar integrated circuit utilizing Jean Hoerni's planar process, filing US Patent 2,981,877 in July 1959. Kilby filed this patent (US 3,138,743) on February 6, 1959. A bitter ten-year patent battle ensued over who invented the integrated circuit.

Final Resolution & Judicial Outcome:

The courts affirmed Kilby's priority on the concept of monolithic integration and Noyce's priority on planar thin-film interconnections. Texas Instruments and Fairchild wisely signed a landmark cross-licensing agreement in 1966, sharing royalties and allowing the microelectronics industry to explode globally.

Civilizational Impact

Kilby's integrated circuit made the digital revolution possible. It enabled the Apollo Guidance Computer, personal computers, the internet, smartphones, medical MRI machines, global satellite navigation, and modern artificial intelligence.

Historical Fact

Kilby built his first integrated circuit in the summer of 1958 because Texas Instruments had a company-wide mass vacation policy for all employees, but as a new hire, Kilby had not earned any vacation days and was left completely alone in the semiconductor laboratory.