About this previous year paper
Section A – Basic Concept Questions (Description)
Section A contains short conceptual questions related to the fundamental processes used in Integrated Circuit (IC) fabrication. These questions test the basic understanding of semiconductor manufacturing techniques such as diffusion, annealing, etching, oxidation, and ion implantation.
Students are expected to give short explanations of these processes and understand their importance in the fabrication of integrated circuits. The section also includes topics such as photoresist materials, silicon dioxide properties, auto-doping, and IC packaging, which are essential parts of semiconductor device manufacturing.
The purpose of this section is to check whether students understand the basic terminology and processes used in microelectronics fabrication technology. A clear understanding of these concepts helps students learn how electronic components are built on silicon wafers.
Questions for Section A
What is diffusion in semiconductor fabrication?
What is meant by annealing?
What is a negative photoresist?
What is auto-doping?
What is etching in IC fabrication?
List the important properties of oxide layers.
Explain the importance of silicon dioxide in IC fabrication.
Classify integrated circuits on the basis of their complexity.
What is IC packaging?
List the advantages of ion implantation.
Section B – Descriptive Questions (Description)
Section B consists of descriptive and analytical questions that require detailed explanations of semiconductor fabrication processes. Students must explain theoretical principles, fabrication techniques, and measurement methods used in integrated circuit manufacturing.
One important topic in this section is Fick’s laws of diffusion, which describe how impurity atoms spread inside semiconductor materials during doping. Students are required to derive and explain these laws.
Another major topic is thin film deposition, where materials are deposited onto semiconductor wafers using techniques such as Physical Vapour Deposition (PVD) and Chemical Vapour Deposition (CVD). Students must explain the characteristics required for high-quality thin films.
The section also covers etching techniques, including wet chemical etching and the different chemical solutions used to etch materials such as silicon, silicon dioxide, and silicon nitride.
Students must also understand polysilicon gate technology, which replaced metal gate technology in MOSFET fabrication due to its advantages in device performance.
Questions for Section B
State and explain Fick’s first law of diffusion and derive Fick’s second law.
What are thin films? Explain a physical vapour deposition technique and its characteristics.
Explain the Atmospheric Pressure Chemical Vapour Deposition (APCVD) system with advantages and disadvantages.
What is wet chemical etching? List common etchants used for Si, SiO₂, and Si₃N₄.
Explain the advantages of polysilicon gate technology over metal gate technology and its fabrication process.
What is sheet resistance? Explain the four-point probe method for measuring sheet resistance.
Calculate the time required for silicon dioxide growth under given oxidation conditions.
Explain the kinetics of oxide growth and why MOSFETs are fabricated on (100) oriented silicon substrates.
Section C – Advanced Analytical Questions (Description)
Section C includes long analytical questions that require detailed explanations of advanced IC fabrication techniques and materials used in semiconductor manufacturing.
One of the main topics in this section is ion implantation, which is a technique used to introduce impurity atoms into semiconductor materials. Students must explain why ion implantation is preferred over diffusion for doping and describe the ion implantation process with diagrams.
Another important topic is metallization, which is used to create electrical connections between different components on a semiconductor chip. Students must explain the materials used for metallization and the advantages of silicide technology.
The section also includes sputtering techniques, which are used for depositing refractory materials like tantalum. Students must explain the working principle of D.C. sputtering and illustrate the process with diagrams.
These questions evaluate the student’s understanding of advanced semiconductor fabrication technologies used in modern integrated circuit manufacturing.
Questions for Section C
What is ion implantation? Why is it preferred over diffusion for impurity doping? Explain the technique with a labeled diagram.
Explain metallization in integrated circuits. Discuss silicide technology and list the metals used in silicidation.
Why is sputtering used for deposition of refractory materials? Explain the D.C. sputtering technique with a diagram.