Overview of Semiconductor Materials

As an important link in the upstream of the semiconductor industry chain, semiconductor materials play a key role in the manufacturing process of chips. According to the chip manufacturing process, semiconductor materials are mainly divided into matrix materials, manufacturing materials and packaging materials. Among them, the base material is mainly used to manufacture silicon wafers or compound semiconductors; the manufacturing materials are mainly various materials required for processing silicon wafers or compound semiconductors into chips; the packaging materials are used in the process of packaging and cutting the prepared chips. to the material.

Base material: According to different chip materials, base materials are mainly divided into silicon wafers and compound semiconductors. Among them, silicon wafers are the most widely used and are the most important raw materials in the manufacturing process of integrated circuits.

1. Silicon wafer

The silicon wafers are all monocrystalline silicon wafers, and the purity of the silicon material is relatively high. Generally, the purity of the silicon wafers is required to be above 99.9999999%, so the manufacturing barrier is relatively high. Generally speaking, the larger the wafer size, the smaller the edge loss of wafer cutting, the more chips that can be cut per wafer, the higher the semiconductor production efficiency, and the lower the corresponding cost.

2. Compound semiconductors

It mainly refers to the second and third generation semiconductors such as gallium arsenide (GaAs), gallium nitride (GaN), and silicon carbide (SiC). Among compound semiconductors, gallium arsenide (GaAs) has the characteristics of high power density, low energy consumption, high temperature resistance, high luminous efficiency, radiation resistance, and high breakdown voltage, and is widely used in radio frequency, power devices, microelectronics, optoelectronics and defense and military industries. and other fields. Gallium Nitride (GaN) can carry higher energy density and has higher reliability. It is used in communication fields such as mobile phones, satellites, and aerospace, as well as in non-communication fields such as optoelectronics, microelectronics, high-temperature and high-power devices, and high-frequency microwave devices. Has a wide range of applications; silicon carbide (SiC) has the characteristics of high forbidden band width, high saturation electron drift speed, high thermal conductivity, etc. The application is more extensive.

Manufacturing Materials

1. Photoresist

Photoresist is the core material of the lithography process. It is mainly an etching-resistant material whose solubility changes through irradiation or radiation of light sources such as ultraviolet light, excimer laser, electron beam, ion beam, and X-ray. According to different downstream application scenarios, photoresist can be divided into semiconductor photoresist, LCD photoresist and PCB photoresist. From the perspective of composition, the main components of photoresist include photoresist resin, sensitizer, solvent and additives.

In the photolithography process, the photoresist is smeared on the substrate. After the light or radiation is irradiated to the substrate through the mask, the solubility of the photoresist in the developing solution changes. After the solution dissolves the soluble part, The photoresist layer forms the exact same pattern as the mask, and then the pattern transfer is completed on the substrate by etching. Depending on the downstream application, the substrates can be printed circuit boards, panels and integrated circuit boards. The lithography process is the core process in semiconductor manufacturing.

2. Sputtering target

The target material is an indispensable raw material for the sputtering process of preparing electronic thin film materials. The sputtering process mainly uses the ions generated by the ion source to accelerate the ion beams gathered into a high-speed flow in a vacuum to bombard the solid surface, so that the atoms on the solid surface leave the solid and deposit on the surface of the substrate. The bombarded solid is called sputtering. target.

Sputtering targets are mainly used in the fields of semiconductors, flat panel displays and solar cells. Semiconductors have the highest requirements on the metal purity and internal microstructure of the target, usually requiring more than 99.9995% (5N5), while the metal purity requirements for flat panel displays and solar cells are relatively low, requiring 99.999% (5N) and 99.995% (4N5) respectively. )above.

3. Polishing material

The working principle of chemical mechanical polishing (CMP) is that in the presence of a certain pressure and polishing liquid, the polished wafer and the polishing pad move relative to each other. The organic combination makes the polished wafer surface meet the requirements of high flatness, low surface roughness and low defect.

Polishing pad and polishing liquid are the most important polishing materials. Among them, polishing liquid is a water-soluble polishing agent without any sulfur, phosphorus and chlorine additives. It mainly plays the role of polishing, lubricating and cooling, while polishing pad is mainly used for polishing. It stores and transmits the polishing liquid, provides a certain pressure to the silicon wafer and mechanically rubs the surface, and is an important auxiliary material that determines the surface quality.

4. Electronic special gas

Electronic special gas (referred to as "electronic special gas") is the second largest semiconductor raw material after silicon wafer, and is widely used in downstream applications. Electronic special gas refers to pure gas, high-purity gas or binary or multi-component mixed gas ( The specific products are shown in the figure below). Electronic special gas is a key chemical material in the electronics industry, and its downstream applications include semiconductors, display panels, fiber optic cables, photovoltaics, new energy vehicles, aerospace and other fields.

5. Mask

Also known as photomask, photomask, and lithography mask, it is the carrier of the design pattern in the lithography process of semiconductor chips. Through lithography and etching, the pattern is transferred to the silicon wafer. Usually, different glass substrates are selected according to different needs.

6. Wet electronic chemicals

Also known as ultra-clean and high-purity reagents, it is mainly used for various high-purity chemical reagents in the semiconductor manufacturing process. According to the purpose, it can be divided into general wet electronic chemicals and functional wet electronic chemicals, among which general wet electronic chemicals generally refer to high-purity pure chemical solvents, such as high-purity deionized water, hydrofluoric acid, sulfuric acid, phosphoric acid, nitric acid and other more common reagents. Functional wet electronic chemicals refer to formula chemicals that achieve special functions through compounding methods and meet special process requirements in the manufacturing process, such as developer, stripper, cleaning solution, etching solution, etc., which are often used in etching, Sputtering and other process links. In the wafer manufacturing process, high-purity chemical solvents are mainly used to clean pollutants such as particles, organic residues, metal ions, and natural oxide layers.

Packaging Material

1. Bonding material

The material used to realize the connection between the die and the base or the package substrate by bonding technology must meet the requirements of high mechanical strength, stable chemical properties, electrical and thermal conductivity, low curing temperature and strong operability in terms of physical and chemical properties. The main bonding technologies in practical applications include silver paste bonding technology, low melting point glass bonding technology, conductive adhesive bonding technology, epoxy resin bonding technology, and eutectic welding technology. Epoxy resin is a widely used bonding material. The surface of the chip and the basic packaging material has different hydrophilic and hydrophobic properties. Plasma treatment is required to improve the fluidity of the epoxy resin on the surface and improve the bonding effect. .

2. Ceramic packaging materials

Functions such as mechanical support, environmental sealing and heat dissipation for carrying electronic components. Compared with metal encapsulation materials and plastic encapsulation materials, ceramic encapsulation materials have good moisture resistance, good linear expansion rate and thermal conductivity, and have extremely stable performance in electrothermal and mechanical aspects, but have high processing costs and high brittleness.

3. Package substrate

It is the part with the largest cost in the packaging material, which mainly plays the role of carrying the protection chip and connecting the upper chip and the lower circuit board. A complete chip is composed of a bare chip (wafer) and a package (package substrate, sealing material, leads, etc.). The packaging substrate can protect, fix, and support the chip, enhance the thermal conductivity and heat dissipation performance of the chip, and can also connect the chip and the printed circuit board to achieve electrical and physical connection, power distribution, signal distribution, and communication between the internal and external circuits of the chip and other functions.

4. Cutting material

Wafer dicing is an important process in the semiconductor chip manufacturing process. It belongs to the latter process in wafer manufacturing. It mainly cuts the entire wafer with the chip into a single chip well according to the size of the chip. In the packaging process, dicing is the pre-process of wafer testing. The common chip packaging process is to first cut the entire wafer into small dies and then perform packaging testing, while the wafer-level packaging technology is the whole wafer. After packaging and testing, a single finished chip is obtained by cutting.

The current mainstream cutting methods are divided into two categories, one is cutting with a dicing system, and the other is cutting with a laser. Among them, dicing system cutting mainly includes mortar cutting and diamond material cutting. This technology started early and has a large market share. Laser cutting is an emerging non-contact cutting, and the cutting surface is smooth and flat, which is suitable for different types of wafer cutting.