Implantation In Semiconductor
Ion implantation is a doping method that is used in semiconductors that introduce impurities into a semiconductor wafer.
How is ion implantation typically performed?
Ion implantation is carried out by implanting energetic dopant ions into the semiconductor using an ion beam. The profile of the dopant distribution is mainly determined by the ion mass and energy. Implantation energies typically range from 1 keV to 1 MeV, resulting in ion distributions with average depths ranging from 10 nm to 10 µm.
What are the advantages of ion implantation over the diffusion process in semiconductor manufacturing?
The main advantages of ion implantation are its more precise control and reproducibility of impurity dopings and its lower processing temperature compared to the diffusion process.
What is the principal side effect of ion implantation?
The principal side effect of ion implantation is the disruption or damage of the semiconductor lattice due to ion collisions. This damage is mitigated by subjecting the semiconductor to a subsequent annealing treatment to remove the lattice disruptions.
What are the common methods of physical vapor deposition (PVD) for depositing metals?
The common methods of PVD include evaporation, electron-beam evaporation, plasma spray deposition, and sputtering.
How does evaporation work as a PVD method?
Evaporation involves heating the source material above its melting point in an evacuated chamber. The source material can be melted using resistance heating, radio frequency (RF) heating, or a focused electron beam (e-beam).
Why have evaporation and e-beam evaporation been largely replaced by sputtering for modern integrated circuits (ICs)?
Evaporation and e-beam evaporation have been replaced by sputtering for modern ICs due to sputtering’s advantages in terms of deposition rate, control, and efficiency.
Describe the ion-beam sputtering process and its benefits compared to other PVD methods.
Ion-beam sputtering involves accelerating ions toward a target’s surface, causing material to be sputtered onto a wafer. Benefits include independent control of ion current and energy and reduced contamination due to lower chamber pressure.
What are some techniques used to increase the deposition rate and control the angular distribution in sputtering?
Techniques to increase deposition rate include using a third electrode to provide more electrons for ionization and employing a magnetic field, such as in magnetron sputtering. Long-throw sputtering is used to control the angular distribution by addressing factors like target-substrate separation and gas scattering.
Chemical–Chemical-mechanical polishing (CMP) in Semiconductor Manufacturing
Chemical–Mechanical Polishing (CMP) has emerged as a crucial technology in multilevel interconnection processes within semiconductor manufacturing. Its significance lies in its unique ability to achieve global planarization, ensuring a flat surface across the entire semiconductor wafer. This is particularly vital for creating intricate circuitry and interconnections in modern semiconductor devices.
Advantages of CMP
- Global Planarization: CMP stands out as the sole method capable of achieving global planarization, essential for creating uniform and precise semiconductor structures.
- Defect Density Reduction: CMP offers advantages in terms of reduced defect density, contributing to the overall yield and reliability of semiconductor devices.
- Avoidance of Plasma Damage: Unlike planarization systems based on Reactive Ion Etching (RIE), CMP eliminates the risk of plasma damage to the semiconductor material.
Components of the CMP Process
The CMP process involves dynamic interactions between three main components:
- Sample Surface: This is the semiconductor wafer’s surface that undergoes the polishing process. CMP selectively removes material from elevated regions, ensuring a flat surface.
- Polishing Pad: The pad is a critical element that facilitates the transfer of mechanical action to the sample surface. It plays a key role in controlling the material removal rate and surface uniformity.
- Slurry: The slurry is a mixture containing abrasive particles. As the pad moves against the sample surface, abrasive particles in the slurry induce mechanical damage, facilitating enhanced chemical attack. Additionally, loose material is fractured and forms a slurry, aiding in material removal.