First, put polycrystalline silicon and dopants into the quartz crucible in the single crystal furnace, raise the temperature to more than 1000 degrees, and obtain polycrystalline silicon in a molten state.
Silicon ingot growth is a process of making polycrystalline silicon into single crystal silicon. After the polycrystalline silicon is heated into liquid, the thermal environment is precisely controlled to grow into high-quality single crystals.
Related concepts:
Single crystal growth: After the temperature of the polycrystalline silicon solution is stable, the seed crystal is slowly lowered into the silicon melt (the seed crystal will also be melted in the silicon melt), and then the seed crystal is lifted up at a certain speed for the seeding process. Then, the dislocations generated during the seeding process are eliminated through the necking operation. When the neck is shrunk to a sufficient length, the diameter of the single crystal silicon is enlarged to the target value by adjusting the pulling speed and temperature, and then the equal diameter is maintained to grow to the target length. Finally, in order to prevent the dislocation from extending backward, the single crystal ingot is finished to obtain the finished single crystal ingot, and then it is taken out after the temperature is cooled.
Methods for preparing single crystal silicon: CZ method and FZ method. The CZ method is abbreviated as the CZ method. The characteristic of the CZ method is that it is summarized in a straight-cylinder thermal system, using graphite resistance heating to melt the polycrystalline silicon in a high-purity quartz crucible, and then inserting the seed crystal into the melt surface for welding, while rotating the seed crystal, and then reversing the crucible. The seed crystal is slowly lifted upward, and after the processes of seeding, enlargement, shoulder rotation, equal diameter growth, and tailing, a single crystal silicon is obtained.
The zone melting method is a method of using polycrystalline ingots to melt and crystallize semiconductor crystals in different areas. Thermal energy is used to generate a melting zone at one end of the semiconductor rod, and then a single crystal seed crystal is welded. The temperature is adjusted to make the melting zone slowly move to the other end of the rod, and through the entire rod, a single crystal is grown, and the crystal orientation is the same as that of the seed crystal. The zone melting method is divided into two types: horizontal zone melting method and vertical suspension zone melting method. The former is mainly used for the purification and single crystal growth of materials such as germanium and GaAs. The latter is to use a high-frequency coil in an atmosphere or vacuum furnace to generate a molten zone at the contact between the single crystal seed crystal and the polycrystalline silicon rod suspended above it, and then move the molten zone upward to grow a single crystal.
About 85% of silicon wafers are produced by the Czochralski method, and 15% of silicon wafers are produced by the zone melting method. According to the application, the single crystal silicon grown by the Czochralski method is mainly used to produce integrated circuit components, while the single crystal silicon grown by the zone melting method is mainly used for power semiconductors. The Czochralski method has a mature process and is easier to grow large-diameter single crystal silicon; the zone melting method melt does not contact the container, is not easy to be contaminated, has a higher purity, and is suitable for the production of high-power electronic devices, but it is more difficult to grow large-diameter single crystal silicon, and is generally only used for 8 inches or less in diameter. The video shows the Czochralski method.
Due to the difficulty in controlling the diameter of the single crystal silicon rod in the process of pulling the single crystal, in order to obtain silicon rods of standard diameters, such as 6 inches, 8 inches, 12 inches, etc. After pulling the single crystal, the diameter of the silicon ingot will be rolled and ground. The surface of the silicon rod after rolling is smooth and the size error is smaller.
Using advanced wire cutting technology, the single crystal ingot is cut into silicon wafers of suitable thickness through slicing equipment.
Due to the small thickness of the silicon wafer, the edge of the silicon wafer after cutting is very sharp. The purpose of edge grinding is to form a smooth edge and it is not easy to break in the future chip manufacturing.
LAPPING is to add the wafer between the heavy selection plate and the lower crystal plate, and apply pressure and rotate with the abrasive to make the wafer flat.
Etching is a process to remove the surface damage of the wafer, and the surface layer damaged by physical processing is dissolved by chemical solution.
Double-sided grinding is a process to make the wafer flatter and remove small protrusions on the surface.
RTP is a process of rapidly heating the wafer in a few seconds, so that the internal defects of the wafer are uniform, metal impurities are suppressed, and abnormal operation of the semiconductor is prevented.
Polishing is a process that ensures the surface smoothness through surface precision machining. The use of polishing slurry and polishing cloth, combined with appropriate temperature, pressure and rotation speed, can eliminate the mechanical damage layer left by the previous process and obtain silicon wafers with excellent surface flatness.
The purpose of cleaning is to remove organic matter, particles, metals, etc. remaining on the surface of the silicon wafer after polishing, so as to ensure the cleanliness of the silicon wafer surface and meet the quality requirements of the subsequent process.
The flatness & resistivity tester detects the silicon wafer after polishing and cleaning to ensure that the thickness, flatness, local flatness, curvature, warpage, resistivity, etc. of the polished silicon wafer meet customer needs.
PARTICLE COUNTING is a process for precisely inspecting the surface of the wafer, and the surface defects and quantity are determined by laser scattering.
EPI GROWING is a process for growing high-quality silicon single crystal films on polished silicon wafers by vapor phase chemical deposition.
Related concepts: Epitaxial growth: refers to the growth of a single crystal layer with certain requirements and the same crystal orientation as the substrate on a single crystal substrate (substrate), just like the original crystal extending outward for a section. Epitaxial growth technology was developed in the late 1950s and early 1960s. At that time, in order to manufacture high-frequency and high-power devices, it was necessary to reduce the collector series resistance, and the material was required to withstand high voltage and high current, so it was necessary to grow a thin high-resistance epitaxial layer on a low-resistance substrate. The new single crystal layer grown epitaxially can be different from the substrate in terms of conductivity type, resistivity, etc., and multi-layer single crystals of different thicknesses and requirements can also be grown, thereby greatly improving the flexibility of device design and the performance of the device.
Packaging is the packaging of the final qualified products.
Post time: Nov-05-2024