Semiconductor Supplier and Distributor in the United States 

Semiconductor Materials – What Are Semiconductor Materials?

Materials whose electrical conductivity lies between that of conductors and insulators are called semiconductors. Semiconductor materials are a type of electronic material that possesses semiconductor properties and can be used to manufacture semiconductor devices and integrated circuits. Their resistivity ranges from 10⁻³ to 10⁻⁹ ohm·cm. The electrical properties of semiconductor materials are highly sensitive to external factors such as light, heat, electricity, and magnetism. By introducing small amounts of impurities, the electrical conductivity of these materials can be controlled. It is precisely these properties of semiconductor materials that allow for the creation of multifunctional semiconductor devices.

Semiconductor materials are the foundation of the semiconductor industry, and their development greatly influences the advancement of semiconductor technology. According to their chemical composition and internal structure, semiconductor materials can be roughly divided into the following categories:

1. Elemental semiconductors include germanium, silicon, selenium, boron, tellurium, antimony, etc. In the 1950s, germanium dominated the semiconductor market. However, due to its poor high-temperature resistance and radiation tolerance, it was gradually replaced by silicon in the late 1960s. Silicon-based semiconductor devices offer better performance in terms of temperature and radiation resistance and are particularly suitable for manufacturing high-power devices. Therefore, silicon has become the most widely used semiconductor material, and most of today’s integrated circuits are made from silicon.

2. Compound semiconductors are made from two or more elements. There are many types, with important ones including gallium arsenide, indium phosphide, indium antimonide, silicon carbide, cadmium sulfide, and gallium arsenide silicon. Gallium arsenide is a key material for microwave devices and integrated circuits. Silicon carbide, due to its strong radiation resistance, high temperature endurance, and chemical stability, is widely used in aerospace technology.

3. Amorphous semiconductor materials: Glass used as a semiconductor is a type of amorphous semiconductor material, categorized as oxide or non-oxide glass. These materials have good switching and memory characteristics and strong radiation resistance. They are mainly used to manufacture threshold switches, memory switches, and solid-state display devices.

4. Organic semiconductor materials: Dozens of organic semiconductor materials are known, including naphthalene, anthracene, polyacrylonitrile, phthalocyanine, and some aromatic compounds. These are still in the research phase and not yet widely applied.

Characteristics and Parameters
The conductivity of semiconductor materials is extremely sensitive to trace amounts of impurities. High-purity semiconductor materials are called intrinsic semiconductors and have very high resistivity at room temperature, making them poor conductors. When suitable impurities are added to high-purity semiconductor materials, they provide conductive charge carriers, greatly reducing the resistivity. These doped semiconductors are called extrinsic semiconductors. If the conductivity is mainly due to conduction band electrons, the material is called an N-type semiconductor; if it is due to valence band holes, it is called a P-type semiconductor. When different types of semiconductors are joined (forming a PN junction) or a semiconductor contacts a metal, a diffusion process occurs due to the concentration difference of electrons (or holes), forming a potential barrier at the junction. This junction exhibits unidirectional conductivity. Utilizing the unidirectional conductivity of PN junctions, various functional semiconductor devices can be made, such as diodes, transistors, thyristors, etc. In addition, the conductivity of semiconductor materials is highly sensitive to external conditions (such as heat, light, electricity, magnetism), allowing the production of various sensors for information conversion.

Characteristic parameters of semiconductor materials include bandgap width, resistivity, carrier mobility, minority carrier lifetime, and dislocation density.
The bandgap width is determined by the electronic state and atomic configuration of the semiconductor and reflects the energy needed to excite valence electrons from a bound state to a free state.
Resistivity and carrier mobility reflect the material’s electrical conductivity.
Minority carrier lifetime reflects the relaxation characteristics of carriers transitioning from a non-equilibrium state to an equilibrium state under external influences (e.g., light or electric fields).
Dislocations are one of the most common defects in crystals. Dislocation density measures the lattice integrity of semiconductor single crystal materials. Amorphous semiconductors do not have this parameter.
These parameters not only distinguish semiconductor materials from non-semiconductors but also reveal performance differences between different types of semiconductor materials or the same material under different conditions.


Types
Common semiconductor materials are divided into elemental semiconductors and compound semiconductors.
Elemental semiconductors are made of a single element, mainly silicon, germanium, and selenium, with silicon and germanium being the most widely used.
Compound semiconductors are categorized into binary, ternary, multi-component, and organic compound semiconductors.
Binary compound semiconductors include:
III-V group: gallium arsenide, gallium phosphide, indium phosphide, etc.
II-VI group: cadmium sulfide, cadmium selenide, zinc telluride, zinc sulfide, etc.
IV-VI group: lead sulfide, lead selenide, etc.
IV-IV group: silicon carbide
Ternary and multi-component semiconductors are mainly solid solutions, such as gallium-aluminum-arsenide and gallium-germanium-arsenide-phosphide solid solutions.
Organic compound semiconductors include naphthalene, anthracene, polyacrylonitrile, etc., and are still in the research stage.
In addition, amorphous and liquid semiconductor materials exist, which differ from crystalline semiconductors in that they lack a strictly periodic crystal structure.

Preparation
Different semiconductor devices require semiconductor materials in different forms, including single-crystal slices, wafers, polished slices, and thin films. These forms correspond to different processing technologies. Common semiconductor material preparation processes include purification, single-crystal growth, and epitaxial thin film growth.
All semiconductor materials require raw material purification, with purity levels above six nines (99.9999%), and up to eleven nines (99.999999999%) in some cases.

Purification methods fall into two categories:
Physical purification: does not change the chemical composition of the material.
Chemical purification: involves converting the element into a compound for purification and then reducing it back into an element.

Physical methods include vacuum evaporation, zone refining, and crystal pulling, with zone refining being the most widely used.
Chemical purification involves electrolysis, complexation, extraction, distillation, with distillation being the most commonly used. Since each method has limitations, several purification processes are often combined to obtain qualified materials.
Most semiconductor devices are fabricated on single-crystal wafers or epitaxial wafers based on single crystals.
Batch production of semiconductor single crystals is mainly done using melt growth methods.
The Czochralski method is the most widely used; 80% of silicon crystals, most germanium, and indium antimonide crystals are produced this way. Silicon single crystals can now reach diameters of up to 300 mm.
Magnetic Czochralski involves introducing a magnetic field into the melt to produce highly uniform silicon crystals.
The liquid encapsulated Czochralski method adds a liquid sealant to the surface of the melt, used for growing crystals like gallium arsenide and indium phosphide, which have high decomposition pressures.
The floating zone method avoids container contact and is used to grow ultra-pure silicon crystals.
The horizontal zone refining method is used for producing germanium crystals.
Horizontal directional solidification is mainly for gallium arsenide, while vertical directional solidification is for cadmium telluride and gallium arsenide.
Crystals made by various methods undergo processes like orientation, grinding, notching, slicing, lapping, chamfering, polishing, etching, cleaning, inspection, and packaging to produce finished wafers.
Growing single-crystal thin films on a single-crystal substrate is called epitaxy.
Epitaxial methods include vapor phase, liquid phase, solid phase, and molecular beam epitaxy.
Chemical vapor deposition (CVD) is the primary method for industrial production.
Liquid phase epitaxy (LPE) is also commonly used.
Metal-organic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE) are used for fabricating quantum wells and superlattices.
Amorphous, microcrystalline, and polycrystalline thin films are typically formed on glass, ceramics, or metal substrates using various types of CVD, magnetron sputtering, and other methods.
 

Semiconductor Packaging – What Does Semiconductor Packaging Mean?

Introduction to Semiconductor Packaging:

The semiconductor production process consists of wafer fabrication, wafer testing, chip packaging, and post-packaging testing. Semiconductor packaging refers to the process of converting tested wafers into individual chips according to product models and functional requirements. The packaging process includes: wafers from the front-end process are cut into small dies through dicing, then these dies are mounted onto the corresponding base (lead frame) island using adhesive. Ultra-fine metal (gold, tin, copper, aluminum) wires or conductive resins are then used to connect the bond pads on the chip to the corresponding leads on the substrate, forming the required circuit. The individual dies are then encapsulated with plastic housing for protection. After molding, a series of operations follow, such as post mold cure, trim & form, plating, and printing. Once packaging is completed, final testing is conducted, including incoming inspection, functional testing, and packing, before final warehousing and shipment. The typical packaging process flow is: dicing → die attach → wire bonding → molding → de-flash → plating → marking → trim & form → visual inspection → final test → packing & shipment.

 

Overview of Semiconductor Device Packaging:

Electronic products are composed of semiconductor devices (integrated circuits and discrete components), printed circuit boards, wires, chassis, housing, and display units. Among them, integrated circuits are responsible for signal processing and control, discrete components usually amplify signals, printed circuit boards and wires connect signals, the chassis and housing provide support and protection, and the display serves as the user interface. Therefore, semiconductor devices are a primary and essential component of electronic products and are often referred to as the "rice of the industry" in the electronics sector.
In the 1960s, China independently developed and produced its first computer, which occupied an area of over 100 m². Today’s portable computers are about the size of a backpack, and future computers may be as small as a pen or even smaller. This dramatic reduction in size and simultaneous increase in functionality is a testament to the advancement of semiconductor technology. The main contributions are:
(1) A significant increase in semiconductor chip integration and improvements in lithography precision in wafer fabrication, allowing chips to become more powerful and compact;
(2) Improvements in semiconductor packaging technology have greatly increased the integration density of integrated circuits on PCBs, significantly reducing the size of electronic products.
Advances in assembly technology are primarily reflected in the evolution of packaging types. Assembly typically refers to the process of using film technology and micro-connection technology to bond semiconductor chips with leadframes, substrates, plastic films, or conductors on PCBs, and to extract connection leads. These are encapsulated using a moldable insulating medium to form a three-dimensional structure. Packaging provides electrical connectivity, physical support and protection, shielding from external interference, stress buffering, heat dissipation, dimensional transformation, and standardization. From the DIP packages of the transistor era, to the surface-mount packages of the 1980s, and now to module and system-in-package (SiP) technologies, many packaging types have been developed. Each new packaging form may require new materials, processes, or equipment.
The driving force behind the continuous evolution of semiconductor packaging forms is price and performance. The electronics market has three main customer types: consumer, industrial, and government users

Consumer users prioritize low cost and can tolerate moderate performance.
Government users (such as military and aerospace) require high performance and are willing to pay prices tens to thousands of times higher than consumers.
Industrial users fall in between, balancing performance and cost.
Low-cost demands mean minimizing material usage and maximizing yield, while high-performance demands require longer product life, high tolerance to extreme temperatures and humidity. Semiconductor manufacturers constantly strive to reduce costs and enhance performance. Additionally, environmental regulations and patent issues often necessitate packaging changes.
 

Functions of Packaging:

Packaging is essential and critical for chips. Packaging refers to the housing used to encapsulate semiconductor integrated circuit chips. It not only protects the chip and enhances heat dissipation but also serves as a bridge between the chip and external circuits while standardizing interfaces. The main functions of packaging are:
(1) Physical Protection: Chips must be isolated from the external environment to prevent corrosion by airborne impurities, which can degrade electrical performance. Packaging protects the chip surface and bonding wires, shielding the fragile chip from physical and environmental damage. It also aligns the thermal expansion coefficients between the chip and the substrate or lead frame to mitigate stress caused by heat and environmental changes, preventing chip failure. To meet heat dissipation requirements, thinner packages are better. For chips with power consumption over 2W, heatsinks are added to enhance cooling; above 5–10W, forced cooling methods are required. Additionally, packaged chips are easier to install and transport.

(2) Electrical Connection: The dimensional transformation function of packaging converts ultra-fine pitches on chips to the more manageable sizes on PCBs. For instance, chip features may be below 0.13 µm, chip solder points around 10 µm, external leads around 100 µm, and PCB traces in millimeters. Packaging enables this scale transformation, reducing operation costs, materials, and improving reliability. It also helps ensure signal waveform and speed by minimizing connection resistance, parasitic capacitance, and inductance through optimal layout and impedance matching.

(3) Standardization: Packaging dimensions, shapes, number of pins, pitch, and length follow standard specifications, facilitating manufacturing and compatibility with PCBs. Standardization benefits packaging users, PCB manufacturers, and semiconductor vendors. In contrast, bare die mounting and flip-chip bonding currently lack this advantage. The quality of assembly technology also affects chip performance and PCB design/manufacturing. For many IC products, packaging technology is a critical factor.
 

Packaging Classification:

Semiconductors (including ICs and discrete devices) have seen several generations of packaging evolution—from DIP, SOP, QFP, PGA, BGA, MCP to SiP. Each generation advances in performance indicators: chip-to-package area ratio approaching 1, higher operating frequency, better thermal tolerance, more pins, reduced pin pitch, lighter weight, improved reliability, and easier usage. There are numerous types of packaging, each with its own strengths and limitations. The choice of materials, equipment, and technology depends on the specific packaging type and application.