SSI small-scale integration and MSI medium-scale integration integrated circuits (1964-71)

The idea
It was a

Manufacturing
The semi-conductors of the periodic table of the chemical elements were identified as the most likely materials for a solid-state vacuum tube. Starting with copper oxide, proceeding to germanium, then silicon, the materials were systematically studied in the 1940s and 1950s. Today, monocrystalline silicon is the main substrate used for ICs although some III-V compounds of the periodic table such as gallium arsenide are used for specialized applications like LEDs, lasers, solar cells and the highest-speed integrated circuits. It took decades to perfect methods of creating crystals without defects in the crystalline structure of the semiconducting material.

Semiconductor ICs are fabricated in a planar process which includes three key process steps – imaging, deposition and etching. The main process steps are supplemented by doping and cleaning.

Semiconductor device fabrication is the process used to create the integrated circuits that are present in everyday electrical and electronic devices. It is a multiple-step sequence of photo lithographic and chemical processing steps during which electronic circuits are gradually created on a wafer made of pure semiconducting material. Silicon is almost always used, but various compound semiconductors are used for specialized applications.

The entire manufacturing process, from start to packaged chips ready for shipment, takes six to eight weeks and is performed in highly specialized facilities referred to as fabs.

Mono-crystal silicon wafers (or for special applications, silicon on sapphire or gallium arsenide wafers) are used as the substrate. Photolithography is used to mark different areas of the substrate to be doped or to have polysilicon, insulators or metal (typically aluminium) tracks deposited on them.

Integrated circuits are composed of many overlapping layers, each defined by photolithography, and normally shown in different colors. Some layers mark where various dopants are diffused into the substrate (called diffusion layers), some define where additional ions are implanted (implant layers), some define the conductors (polysilicon or metal layers), and some define the connections between the conducting layers (via or contact layers). All components are constructed from a specific combination of these layers.

In a self-aligned CMOS process, a transistor is formed wherever the gate layer (polysilicon or metal) crosses a diffusion layer.

Capacitive structures, in form very much like the parallel conducting plates of a traditional electrical capacitor, are formed according to the area of the "plates", with insulating material between the plates. Capacitors of a wide range of sizes are common on ICs. Meandering stripes of varying lengths are sometimes used to form on-chip resistors, though most logic circuits do not need any resistors. The ratio of the length of the resistive structure to its width, combined with its sheet resistivity, determines the resistance.

More rarely, inductive structures can be built as tiny on-chip coils, or simulated by gyrators. Since a CMOS device only draws current on the transition between logic states, CMOS devices consume much less current than bipolar devices.

Electrical generations
In the early days of simple integrated circuits, the technology's large scale limited each chip to only a few transistors, and the low degree of integration meant the design process was relatively simple. Manufacturing yields were also quite low by today's standards. As the technology progressed, millions, then billions[18] of transistors could be placed on one chip, and good designs required thorough planning, giving rise to new design methods.

The first integrated circuits contained only a few transistors. Early digital circuits containing tens of transistors provided a few logic gates, and early linear ICs such as the Plessey SL201 or the Philips TAA320 had as few as two transistors. The number of transistors in an integrated circuit has increased dramatically since then. The term "large scale integration" (LSI) was first used by IBM scientist Rolf Landauer when describing the theoretical concept;[citation needed] that term gave rise to the terms "small-scale integration" (SSI), "medium-scale integration" (MSI), "very-large-scale integration" (VLSI), and "ultra-large-scale integration" (ULSI). The early integrated circuits were SSI.

SSI circuits were crucial to early aerospace projects, and aerospace projects helped inspire development of the technology. Both the Minuteman missile and Apollo program needed lightweight digital computers for their inertial guidance systems. Although the Apollo guidance computer led and motivated integrated-circuit technology, it was the Minuteman missile that forced it into mass-production. The Minuteman missile program and various other Navy programs accounted for the total $4 million integrated circuit market in 1962, and by 1968, U.S. Government space and defense spending still accounted for 37% of the $312 million total production. The demand by the U.S. Government supported the nascent integrated circuit market until costs fell enough to allow firms to penetrate the industrial, and eventually, the consumer markets. The average price per integrated circuit dropped from $50.00 in 1962 to $2.33 in 1968. Integrated circuits began to appear in consumer products by the turn of the decade, a typical application being FM inter-carrier sound processing in television receivers.

The first MOS chips were small-scale integration chips for NASA satellites.

The next step in the development of integrated circuits, taken in the late 1960s, introduced devices which contained hundreds of transistors on each chip, called "medium-scale integration" (MSI).

In 1964, Frank Wanlass demonstrated a single-chip 16-bit shift register he designed, with an incredible (at the time) 120 transistors on a single chip.

MSI devices were attractive economically because while they cost little more to produce than SSI devices, they allowed more complex systems to be produced using smaller circuit boards, less assembly work (because of fewer separate components), and a number of other advantages.

Further development, driven by the same economic factors, led to "large-scale integration" (LSI) in the mid-1970s, with tens of thousands of transistors per chip.

SSI and MSI devices often were manufactured by masks created by hand-cutting Rubylith. An engineer would inspect and verify the completeness of each mask. LSI devices contain so many transistors, interconnecting wires, and other features that it is considered impossible for a human to check the masks or even do the original design entirely by hand. The engineer depends on computer programs and other hardware aids to do most of this work.

Integrated circuits such as 1K-bit RAMs, calculator chips, and the first microprocessors, that began to be manufactured in moderate quantities in the early 1970s, had under 4000 transistors. True LSI circuits, approaching 10,000 transistors, began to be produced around 1974, for computer main memories and second-generation microprocessors.

Casing
In electronics manufacturing, integrated circuit packaging is the final stage of semiconductor device fabrication, in which the tiny block of semiconducting material is encapsulated in a supporting case that prevents physical damage and corrosion. The case, known as a "package", supports the electrical contacts which connect the device to a circuit board.

In the integrated circuit industry, the process is often referred to as packaging. Other names include semiconductor device assembly, assembly, encapsulation or sealing.

The packaging stage is followed by testing of the integrated circuit.

The term is sometimes confused with electronic packaging, which is the mounting and interconnecting of integrated circuits (and other components) onto printed-circuit boards.

A metal can with epoxy inside sits over the IC that is on a epoxy pad. The legs are metal and attach to the IC with thin gold wires. Some were fully encased in epoxy or in a metal can filled with argon, sand or epoxy.

The earliest integrated circuits were packaged in ceramic flat packs, which the military used for many years for their reliability and small size. Commercial circuit packaging quickly moved to the dual in-line package (DIP), first in ceramic and later in plastic. In the 1980s VLSI pin counts exceeded the practical limit for DIP packaging, leading to pin grid array (PGA) and leadless chip carrier (LCC) packages. Surface mount packaging appeared in the early 1980s and became popular in the late 1980s, using finer lead pitch with leads formed as either gull-wing or J-lead, as exemplified by small-outline integrated circuit — a carrier which occupies an area about 30 – 50% less than an equivalent DIP, with a typical thickness that is 70% less.

The next big innovation was the area array package, which places the interconnection terminals throughout the surface area of the package, providing a greater number of connections than previous package types where only the outer perimeter is used. The first area array package was a ceramic pin grid array package.Not long after, the plastic ball grid array (BGA), another type of area array package, became one of the most commonly used packaging techniques.

In the late 1990s, plastic quad flat pack (PQFP) and thin small-outline packages (TSOP) replaced PGA packages as the most common for high pin count devices, though PGA packages are still often used for microprocessors. However, industry leaders Intel and AMD transitioned in the 2000s from PGA packages to land grid array (LGA) packages.

Ball grid array (BGA) packages have existed since the 1970s, but evolved into Flip-chip ball grid array packages (FCBGA) in the 1990s. FCBGA packages allow for much higher pin count than any existing package types. In an FCBGA package, the die is mounted upside-down (flipped) and connects to the package balls via a substrate that is similar to a printed-circuit board rather than by wires. FCBGA packages allow an array of input-output signals (called Area-I/O) to be distributed over the entire die rather than being confined to the die periphery.

Traces out of the die, through the package, and into the printed circuit board have very different electrical properties, compared to on-chip signals. They require special design techniques and need much more electric power than signals confined to the chip itself.

Recent developments consist of stacking multiple dies in single package called SiP, for System In Package, or three-dimensional integrated circuit. Combining multiple dies on a small substrate, often ceramic, is called an MCM, or Multi-Chip Module. The boundary between a big MCM and a small printed circuit board is sometimes blurry.

Early USSR made integrated circuit. The tiny block of semiconducting material (the "die"), is enclosed inside the round, metallic case (the "package").

Just like vacuum tubes (valves), semiconductor packages standards may be defined by national or international industry associations such as JEDEC, Pro Electron, or EIAJ, or may be proprietary to a single manufacturer.

Also see

 * Science
 * Integrated circuits