What Are Semiconductor Chips? Detailed Internal Structure Explained

Before we explain semiconductor chips, we should first understand two points. First, what is a semiconductor? Second, what is a chip?

Semiconductor

A semiconductor (semiconductor) refers to a material with electrical conductivity between that of an insulator (insulator) and a conductor (conductor) at room temperature. Materials with poor conductivity, such as coal, artificial crystals, amber, ceramics, etc., are generally referred to as insulators. Metals with better conductivity, such as gold, silver, copper, iron, tin, and aluminum, are called conductors. Compared to conductors and insulators, the discovery of semiconductor materials came later; it wasn’t until the 1930s that the industrial world began to pay attention to semiconductors after the purification technology improved. Common semiconductor materials include silicon, germanium, and gallium arsenide, with silicon being the most influential in commercial applications.

Chip

A chip (chip), also known as a microchip (microchip) or integrated circuit (integrated circuit, IC), refers to a silicon wafer containing integrated circuits, which is very small. Generally speaking, chips (ICs) refer to all semiconductor components and are circuit modules that combine various electronic components on a silicon plate to achieve specific functions. They are the most important part of electronic devices, responsible for computation and storage. They are widely used in military, civilian, and almost all electronic devices.

At this point, you probably have a simple understanding of semiconductors and chips. Next, let’s talk about semiconductor chips.

What is a semiconductor chip?

Generally speaking, semiconductors, integrated circuits, and chips can be considered equivalent because they refer to the same thing.

A semiconductor is a type of material, categorized into four types in the table, and due to the high proportion of integrated circuits, exceeding 80%, the industry habitually refers to the semiconductor industry as the integrated circuit industry.

Chips are the carriers of integrated circuits, and in a broad sense, we equate chips with integrated circuits.

So for beginners, just remember that when chips, integrated circuits, and semiconductors appear, don’t panic; it’s the same thing.

Internal Structure of Semiconductor Chips

Although semiconductor chips are small, their internal structure is very complex, especially their core micro-units—thousands of transistors. We will explain the internal structure of semiconductor chip integrated circuits in detail. Generally, we use a structure hierarchy from large to small to understand integrated circuits, which makes it easier to comprehend.

(1) System Level

Taking mobile phones as an example, the entire phone is a complex circuit system; it can play games, make calls, listen to music, and more. Its internal structure consists of multiple semiconductor chips connected with resistors, inductors, and capacitors, referred to as the system level. (Of course, with technological advancements, the technology to integrate an entire system onto a single chip has also existed for many years—SoC technology)

(2) Module Level

The entire system is divided into many functional modules, each with its own responsibilities. Some manage power, some handle communication, some are responsible for display, some for sound, and some for overall computation, etc. We refer to this as the module level. Each of these modules is a vast field, gathering countless human wisdom and sustaining many companies.

(3) Register Transfer Level (RTL)

So what does each module consist of? Taking the digital circuit module, which occupies a large proportion of the entire system (responsible for logical operations, processing discrete signals of 0s and 1s) as an example. It consists of registers and combinational logic circuits.

A register is a circuit structure that can temporarily store logical values, requiring a clock signal to control the duration of the stored logical value.

In practical applications, we need a clock to measure the duration of time, and circuits also require clock signals to coordinate arrangements. The clock signal is a periodically stable rectangular wave. In reality, the ticking of a second is a basic time scale for us, while the oscillation of a rectangular wave in the circuit is a time scale in their world. Circuit components respond accordingly to this time scale, fulfilling their duties.

What is combinational logic? It is a combination of many “AND (与), OR (或), NOT (非)” logic gates. For example, two series-connected light bulbs, each with a switch, will only light up if both switches are on; this is called AND logic.

A complex functional module is precisely composed of numerous registers and combinational logic. This level is called the register transfer level.

(4) Gate Level

The registers in the register transfer level are also constructed from AND and OR logic, and breaking it down further into AND, OR, and NOT logic reaches the gate level (they act like gates, blocking or allowing the entry and exit of electrical signals, hence the name).

(5) Transistor Level

Whether digital circuits or analog circuits, at the lowest level, it reaches the transistor level. All logic gates (AND, OR, NOT, NAND, NOR, XOR, XNOR, etc.) are composed of individual transistors. Therefore, integrated circuits from macro to micro, at the lowest level, are filled with transistors and the wires connecting them.

Bipolar Junction Transistors (BJT) were used more frequently in the early days, commonly known as transistors. They can amplify signals when connected with resistors, power supplies, and capacitors. Like stacking blocks, they can be used to construct various circuits, such as switches, voltage/current source circuits, the aforementioned logic gate circuits, filters, comparators, adders, and even integrators. Circuits constructed with BJTs are referred to as TTL (Transistor-Transistor Logic) circuits. The circuit symbol for BJT looks like this:

However, with the emergence of Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs), which have excellent electrical characteristics and ultra-low power consumption, the IC field has been swept. Besides BJTs still appearing in analog circuits, most integrated circuits today are composed of MOSFETs. Similarly, they can also be used to build thousands of circuit types. Moreover, they can be appropriately connected to serve as basic circuit components like resistors and capacitors. The circuit symbol for MOSFET is as follows:

In summary, in actual industrial production, the manufacturing of chips is essentially the process of manufacturing thousands of transistors. However, in reality, the order of manufacturing chips is reversed, starting from the lowest level of transistors and building up layer by layer.

That is to say, following the order of “transistor -> chip -> circuit board”, we can ultimately obtain the core component of electronic products—the circuit board.

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