Chip manufacturing
The production of chips starts from user needs, and goes through design, manufacturing, packaging, finished product testing and finally leaving the factory. Among them, the most technically difficult is design and manufacturing. Design requires a large number of computer-aided design software, design takes a long time, and it takes a lot of experience to design a good product. Currently, most of the products are refurbished from the versions they were originally designed. Chip manufacturing is the largest part of investment in chip production, and a technologically advanced chip manufacturing plant cannot make products without billions of dollars. In addition to the huge investment, it is necessary to have a large number of experienced technicians to develop a good manufacturing process.
芯片制造一般有五个重要步骤：一是光刻（Photolithography）；二是刻蚀（Etch）；三是薄膜沉积（Deposition）；四是扩散（Diffusion）；五是离子注入（Ion Implantation）。
1. Lithography
Photolithography is similar to traditional photography in that a photoresist is applied to the wafer, then a mask is exposed, a develop photoresist is developed, and the exposed area is etched. As a result, there is an area on the wafer that is etched or implanted. The lithography process is primarily used to define the geometric pattern on a silicon wafer.
1. Coated with photoresist
The first step in drawing a circuit on a wafer is to coat the oxide layer with a photoresist. Photoresist makes the wafer "photo paper" by changing its chemical properties. The thinner the photoresist layer on the wafer surface, the more uniform the coating, and the finer the pattern that can be printed. This step can be done using the "spin coating" method.
According to the difference in light (ultraviolet) reactivity, photoresists can be divided into two types: positive and negative, the former will decompose and disappear after receiving light, leaving a pattern in the unexposed area, and the latter will polymerize after receiving light and make the pattern of the light-receiving part visible.
2. Exposure
Once the wafer is covered with a photoresist film, the circuit can be printed by controlling the light exposure, a process known as "exposure". We can selectively pass light through an exposure device, and as the light passes through a mask containing the circuit pattern, the circuit can be printed onto a wafer coated with a photoresist film underneath.
3. Development
The post-exposure step is to spray a developer on the wafer with the goal of removing the photoresist from areas not covered by the pattern, allowing the printed circuit pattern to be revealed. After the development is completed, it is necessary to check it with various measuring equipment and optical microscopes to ensure the quality of the circuit diagram drawing.
2. Etching
Physical, chemical, or both chemical and physical methods are used to selectively remove the part of the material that is not protected by the mask, so as to obtain a pattern consistent with the mask and realize the pattern transfer.
There are two main methods of etching, depending on the substance used: wet etching using a specific chemical solution to remove the material, and dry etching using gas or plasma.
1. Wet etching
A specific solution is used to chemically react with the material in the unprotected part to form a soluble substance that dissolves in the solution, so that the material is removed from the surface layer by layer
2. Dry etching
Dry etching can be divided into three types: physical etching, chemical etching, and physicochemical bonding (reactive ion etching).
3. Thin film deposition
Thin film deposition is the deposition of material on the surface of a wafer. There are chemical vapor deposition (CVD) and physical vapor deposition (PVD) methods. Chemical vapor deposition is the injection of several gases into a silicon wafer, and the substances are deposited on the wafer after a chemical reaction. Physical vapor deposition is the process of depositing atoms on silicon wafers, which is the process from solid phase to gas phase and then to solid phase.
1. Chemical vapor deposition
In chemical vapor deposition, the precursor gas undergoes a chemical reaction in the reaction chamber and forms a thin film that adheres to the surface of the wafer and is a by-product that is pumped out of the chamber.
2. Physical vapor deposition
Physical vapor deposition refers to the formation of thin films by physical means. Sputtering is a physical vapor deposition method, the principle of which is to sputter out the atoms of the target material through the bombardment of argon plasma and deposit them on the surface of the wafer to form a thin film.
Fourth, diffusion
Diffusion has two roles in chip manufacturing: one is to produce an oxide layer, which is produced at a temperature of 800~1200 °C, and the other is to inject impurities into the silicon wafer or activate it at high temperatures.
5. Ion implantation
Ion implantation is to use the wafer as an electrode, and a high voltage is added between the ion source and the wafer, so that those doped ions will be injected into the wafer with extremely high energy, forming an N- or P-type region on the wafer. After ion implantation, the wafer must be annealed at a high temperature to repair the damage to the wafer after ion implantation. Ion implantation is mainly used to fabricate different semiconductor regions (see figure below for N-region or P-region).