The correct answer is option 'D': Either Diffusion or Ion Implantation Process.

Introduction:
In the fabrication process of semiconductor devices, dopants are introduced into the active areas of silicon to alter its electrical properties. Dopants are impurity atoms added to the semiconductor material to modify its conductivity. The most commonly used dopants in silicon are boron, phosphorus, arsenic, and antimony.

Explanation:

1. Diffusion Process:
- Diffusion is a process in which dopant atoms are introduced into the semiconductor material by creating a concentration gradient.
- In this process, the dopants are first deposited on the surface of the silicon wafer.
- The wafer is then heated at high temperatures, typically in the range of 800-1200 degrees Celsius, in a controlled environment.
- As the wafer is heated, the dopant atoms diffuse into the silicon crystal lattice, replacing some of the silicon atoms.
- The diffusion process continues until the desired concentration and depth of the dopant atoms are achieved.
- The diffusion process is commonly used for introducing low-concentration dopants into the silicon substrate.

2. Ion Implantation Process:
- Ion implantation is a process in which dopant ions are accelerated to high energies and then implanted into the silicon substrate.
- In this process, the dopant ions are generated by ionizing dopant gas molecules using a high-energy source.
- The ions are then accelerated using an electric field and directed towards the silicon wafer.
- The high-energy ions penetrate the surface of the wafer and come to rest at a certain depth.
- The depth of implantation can be controlled by adjusting the energy of the ions.
- After implantation, the wafer is annealed to repair any damage caused by the implantation process and to activate the dopant atoms.
- Ion implantation is a precise and controllable method for introducing both low and high-concentration dopants into the silicon substrate.

Conclusion:
Both the diffusion process and ion implantation process are commonly used in the fabrication of semiconductor devices to introduce dopants into the active areas of silicon. The choice between these processes depends on the specific requirements of the device being fabricated, such as the desired dopant concentration, depth, and profile.