Research of cutting wafer process

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lasercutting
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Research of cutting wafer process

Post by lasercutting » Fri Jul 20, 2018 1:33 am

Silicon wafers are the most important semiconductor materials. At present, more than 90% of chips and sensors are based on semiconductor single-crystal silicon wafers. The laser dicing machine is a model specially designed for the cutting and dicing process of various wafers. Currently, wafers of 6-inch, 8-inch and 12-inch diameter can be cut. The thickness of the cuttable material covers the meters and millimeters. It is a good choice for domestic semiconductor manufacturers.

The laser scribing uses high-energy laser beams to irradiate the surface of the solar cells and silicon wafers. The high peak energy of the laser is used to locally melt and vaporize the irradiated regions. Laser scribing is performed under the control of a numerical control table to achieve scribing. purpose. Equipment advantages: low current, high efficiency, low operating current, and high speed; This device is a model designed for various wafer cutting and dicing processes. Currently, wafers of 6-inch, 8-inch and 12-inch diameter can be cut. The thickness of the cuttable material covers the meters and millimeters. It is a good choice for semiconductor manufacturers in the country. Which is has basic maintenance-free, no material loss, zero failure rate and lower operating costs.

The choice of several light sources is suitable for cutting wafers of different sizes. For example, the cold vaporization cutting method for pulsed picosecond lasers and the thermal melting and cutting methods for fiber lasers can also use YAG light sources that are more cost-effective. Typical Applications: Suitable for dicing and cutting silicon, germanium, gallium arsenide semiconductor materials such as monocrystalline silicon, polycrystalline silicon, amorphous silicon cells, and silicon wafers. In particular, thick sheets (such as AP 0.7mm single-crystal silicon polysilicon;1.2mm amorphous silicon tape, etc.) can also be highly efficient, high-speed, high-quality and low-current cutting.

1.Basic process flow
The silicon ingot is carved into a small gap or a facet to show the crystal orientation. Once inspected, the silicon ingot is cut into wafers. Since silicon is very hard, a diamond saw is used to accurately cut the wafer to get a wafer thicker than the required size. Diamond saws also help reduce damage to wafers, uneven thickness, bending, and warpage defects. After cutting the wafer, it begins to enter the grinding process.
Grind wafers to reduce saw marks and surface damage on the front and back. At the same time thin wafers and help release the stress accumulated during the cutting process. After grinding, the etching and cleaning process is performed and a mixture of sodium hydroxide, acetic acid and nitric acid is used to reduce the damage and cracks generated during the grinding process.
The key chamfering process is to round the edges of the wafers to completely eliminate the possibility of breakage in future circuit fabrication processes. After chamfering, according to the requirements of the end user, it is often necessary to polish the edges to increase the overall cleanliness to further reduce breakage. Polishing (Chemical Mechanical Polishing)is the most important process in the production process is the
polishing of wafers. This process is carried out in a clean room.

Based on the cutting principle: silicon carbide has sharp edges and corners,using silicon carbide abrasive rolling friction, abrasive and cutting silicon block .

Polyethylene glycol (cutting fluid) bonds silicon carbide to the steel wire. The steel wire is conveyed to achieve rolling friction at a certain speed.
Mohs hardness of silicon: 7 Mohs hardness of silicon carbide: 9.0-9.2 Its cleaning principle The chemical equation is: Si+2OH-+H2O==SiO32-+2H2↑
Technological development direction
(1) Application of Single Crystal Slice Reciprocating Cutting Technology
Advantages: save steel wire, uniform thickness of silicon wafer
Difficulties: Solve the influence of the depth and width of the line marks on the printing of the battery, so as to avoid the component appearance failure.
(2) Diamond line and slice technology
Advantage: The TTV of the silicon wafer is greatly improved, reducing the debris and facilitating the thinning.
Difficulties: The surface smoothness of silicon wafers is not as good as that of silicon
carbide, and wire rods and processes need to be optimized.
(3) Silicon technology
Advantages: Avoid kerf loss, high utilization of silicon material.
Difficulties: The silicon wafers grown are small in size, high in defect density, and high in metal content, resulting in low battery efficiency.

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