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Semiconductor processes and equipment: thin film deposition processes and equipment

Thin Film Deposition is to deposit a nano-scale thin film on the substrate, and then repeatedly carry out etching and polishing processes to make many stacked conductive or insulating layers, and each layer has a designed circuit pattern. In this way, semiconductor components and circuits are integrated into chips with complex structures.
thin film deposition

Chemical Vapor Deposition (CVD)

Chemical Vapor Deposition (CVD) forms a thin film on the surface of the substrate through thermal decomposition and/or reaction of gas compounds. The thin film layer materials that can be made by CVD include carbides, nitrides, borides, oxides, sulfides, selenides, tellurides, and some metal compounds, alloys, etc.

Chemical Vapor Deposition is currently a very important micro-manufacturing method because it has the following characteristics:

1. There are many types of deposits: metal films, non-metallic films can be deposited, and multi-component alloy films, as well as ceramic or compound layers can be prepared as required.

2. The CVD reaction is carried out at normal pressure or low vacuum, and the coating has good diffraction, and can be evenly coated on complex-shaped surfaces or deep holes and fine holes in workpieces.

3. It can obtain a thin film coating with high purity, good density, low residual stress and good crystallization. Due to the mutual diffusion of reaction gas, reaction product and substrate, a film layer with good adhesion can be obtained, which is very important for surface passivation, corrosion resistance and wear resistance.

4. Since the temperature of film growth is much lower than the melting point of the film material, a film layer with high purity and complete crystallization can be obtained, which is necessary for some semiconductor films.

5. By adjusting the deposition parameters, the chemical composition, morphology, crystal structure and grain size of the coating can be effectively controlled.

6. The equipment is simple and easy to operate and maintain.

7. The reaction temperature is too high, generally 850~1100℃, and many substrate materials cannot withstand the high temperature of CVD. Plasma or laser assisted technology can be used to reduce the deposition temperature.

The chemical vapor deposition process is divided into three important stages:

1. The reaction gas diffuses to the substrate surface

2. The reaction gas adsorbs on the substrate surface

3. A chemical reaction occurs on the substrate surface to form a solid deposit and the gas phase byproducts are separated from the substrate surface

The most common chemical vapor deposition reactions are:

Thermal decomposition reaction, chemical synthesis reaction and chemical transfer reaction.

The main reaction processes of CVD are as follows:

i). Polysilicon

SiH4 —> Si + 2h2 (600℃)

Deposition rate 100 - 200 nm /min

Phosphorus (phosphine), boron (diborane) or arsenic gas can be added. Polysilicon can also be doped with diffusion gas after deposition.

ii). Silicon dioxide

SiH4 + O2→SiO2 + 2h2 (300 - 500℃)

SiO2 is used as an insulator or passivation layer. Phosphorus is usually added to obtain better electron flow performance.

SiO2 grows thermally when silicon is in the presence of oxygen. The oxygen comes from either oxygen or water vapor. The ambient temperature requirement is 900 ~ 1200℃. 

Both oxygen and water diffuse through the existing SiO2 and combine with Si to form additional SiO2. Water (vapor) diffuses more easily than oxygen, so the growth rate using steam is much faster.

Oxide is used to provide insulation and passivation layers to form transistor gates. Dry oxygen is used to form the gate and thin oxide layer. Steam is used to form thick oxide layers. The insulating oxide layer is usually around 1500nm, and the gate layer is usually between 200nm and 500nm.

Siicon Nitride:

3SiH4 + 4NH3 —> Si3N4 + 12H2

(Silane) (Ammonia) (Nitride)

Chemical Vapor Deposition CVD Equipment

There are three basic types of CVD reactors:

Atmospheric pressure CVD (APCVD)

Low pressure CVD (LPCVD:Low pressure CVD, LPCVD)

Ultrahigh vacuum CVD (UHVCVD:Ultrahigh vacuum CVD)

Laser CVD (LCVD:Laser CVD,)

Metal-organic CVD (MOCVD:Metal-organic CVD)

Plasma-enhanced CVD (PECVD)

The schematic diagram of the low-pressure CVD process is shown in the figure below.
thin film deposition process

The figure below is the structure of an ion-enhanced CVD equipment, which is used to deposit carbon and prepare diamond-like coatings.
As a global top brand of heat treatment equipment manufacturers, Kejia Group specializes in providing thin film deposition processes and equipment for applications in semiconductor, carbon materials, and powder metallurgy industries. It provides high-quality services and equipment to customers around the world. Welcome to consult.


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