What Is a Monolithic Integrated Circuit?

Geisha A. Legazpi

A monolithic integrated circuit (IC) is an electronic circuit that is built on a single semiconductor base material or single chip. Using a single base material is similar to using a blank canvass to create a painting. The surface of the initially neutral semiconductor base will be selectively processed to produce various types of active devices, such as bipolar junction transistors (BJTs) or even field-effect transistors (FETs). A transistor is a three-terminal active device that allows current flow on the main terminals to be controlled.

Monolithic integrated circuits are commonly used as microchips within cellphones.
Monolithic integrated circuits are commonly used as microchips within cellphones.

Usually, a monolithic integrated circuit has a single base semiconductor referred to as a die. For each amplifier IC, each die may have several transistors interconnected to create an electronic circuit that inputs a low-level signal and outputs a scaled-up version, a process called amplification. The square die could be 0.04 inches (1 mm) on each side. At this point, it is emphasized that electronics miniaturization is such that more than a dozen transistors and passive components like resistors and capacitors may fit it an area less than 0.002 square inch (1 square mm).

The die cannot be used alone, because it needs to be interconnected to the “outside world.” A connection is made with very small bonding wires that are fused into the pads in the die. The other end is fused into a lead that will extend to the outside of an IC package. Bonding wires can be as small as two thousandths of an inch and are made of malleable metals such as gold. The most common way to connect the bonding wire to the die pad is by ultrasonic bonding.

In ultrasonic bonding, the bonding wire is pressed into a die pad with a force that presses the wire into the pad along with a sideward periodic displacement at a rate above 25,000 cycles per second or 25 kilohertz (kHz). This prevents damaging the die with excessive heat produced in other methods of bonding to the die. The other end of the bonding wire is fused to the lead frame using the same procedure. The lead frame holds the leads that will be accessible from the outside of a packaged die.

The monolithic integrated circuit is a very common device for manufacturing integrated circuits. Additionally, the monolithic integrated circuit is a commonly used chip or microchip for cell phones, computers, and digital devices. The hybrid IC may use one or more monolithic integrated circuits on a printed circuit board (PCB) along with one or more resistors, capacitors, inductors, and even other active devices such as transistors.

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