Microfabrication Processes Quiz

CMP Advantages

• CMP (chemical mechanical polish) is advantageous in submicron technologies due to its ability to planarize surfaces, remove defects, and enable shallow trench isolation.
• CMP provides a high degree of planarization, reducing the topography of the wafer and enabling the fabrication of multiple layers.

Dry Etch Mechanism

• Dry etch is a process that uses plasma to create reactive species that react with the substrate material to be etched.
• Mean free path is calculated by considering the pressure, temperature, and collision cross-section of the gas molecules.

PVD and CVD Requirements

• Low pressure is necessary for PVD (physical vapor deposition) and CVD (chemical vapor deposition) to reduce the collision frequency between gas molecules and the substrate, allowing for a more controlled deposition process.
• Low pressure also enables the creation of a high-quality film with minimal defects.

Role of Plasma in CVD

• Plasma plays a crucial role in CVD (chemical vapor deposition) by activating the reactant gases, creating a high-density plasma, and enhancing the chemical reactivity of the species.
• The plasma generates a high-energy environment, allowing for the deposition of high-quality films at relatively low temperatures.

Lithography and DOF

• The depth of focus (DOF) is directly proportional to the wavelength (λ) of the exposure light, with shorter wavelengths allowing for a larger DOF.
• A larger DOF enables the creation of smaller critical dimensions (CDs) and improves the overall image quality.

Chemical Amplified Photoresist

• The chemical amplified photoresist mechanism uses a catalyst to amplify the exposure, allowing for a higher sensitivity and improved image quality.
• The catalyst reacts with the exposed areas, generating a strong acid that enhances the solubility of the resist, enabling the creation of high-aspect-ratio patterns.

Step Coverage

• Step coverage refers to the ability of a deposition technique to cover features with varying geometries and aspect ratios.
• Challenges in step coverage include the deposition of uniform films, minimizing defects, and ensuring good adhesion.

Dry Etch vs. Wet Etch

• Dry etch is a plasma-based process that uses reactive species to etch the substrate, offering a high degree of anisotropy and control.
• Wet etch is a chemical-based process that uses a liquid etchant to etch the substrate, offering a higher etch rate but lower anisotropy.

Inline and End of Line Measurements

• Inline measurements include monitoring the fabrication process in real-time, ensuring that the device is meeting the design specifications.
• End of line measurements involve testing the final device to ensure that it meets the required specifications and will last for the specified lifetime.

Analytical Methods for Troubleshooting

• Analytical methods used in semiconductor processing for troubleshooting include SEM (scanning electron microscopy), TEM (transmission electron microscopy), AFM (atomic force microscopy), and XPS (X-ray photoelectron spectroscopy).
• These methods enable the detection and characterization of defects, impurities, and contaminants, allowing for the identification and correction of process issues.