24 Questions
What is the primary purpose of introducing Bottom Anti-Reflection Coatings (BARC) in the patterning process?
To avoid standing waves
What is the effect of trimming on the device pitch?
It has no effect on the device pitch
What is the main reason for using Optical Proximity Correction (OPC) in the patterning process?
To make uniform isolated and dense lines
What is the primary function of Hard-Mask (HM) layers in the patterning process?
To improve the etch process
Why is a second litho step necessary to increase the device density?
Because trimming does not improve the device pitch
What is the origin of Optical Proximity Effects in the patterning process?
The limited amount of higher order spatial frequencies that can pass the lens
What is the main advantage of using multiple exposure in the patterning process?
Enabling the creation of narrow lines at small pitches
What is the purpose of overlaying a new image onto the old one in Self-Aligned Double Patterning (SADP)?
To align the new image with the old one
What is the difference between the double line patterning and double trench approach?
The sequence of litho and etch steps
What is a limitation of using multiple exposure in the patterning process?
Results in a high cost due to multiple litho and etch steps
What is the purpose of using alignment marks in Self-Aligned Double Patterning (SADP)?
To align the new image with the old one
What is the primary benefit of using Optical Proximity Correction (OPC) in the patterning process?
Making uniform isolated and dense lines
What is the primary factor that determines the quality of CD control in a lithography process?
The percentage of dose deviation
What is the maximum dose deviation that can be tolerated while maintaining CD control?
+/- 10% of the target CD
What is the mechanism by which chemical amplification occurs in resist?
Through the action of a photo acid generator
What is the purpose of the post-exposure bake in the lithography process?
To catalyze a chemical reaction using H+
What is the characteristic of a positive tone resist?
It becomes soluble in the developer when exposed
What is the effect of chemical amplification in resist?
It reuses the acid generated multiple times
What is the role of H+ in the chemical reaction during photo acid generator exposure?
To act as a catalyst for deprotection
What is the primary cause of standing waves in photoresist?
Reflection of light in the transparent resist layer
What is the purpose of using a protection group R in the photoresist?
To make the resin insoluble in the base
What is the relationship between the wavelength of light and the total thickness of the resist layer?
The total thickness is equal to λ/4n
What is the nature of the points of no displacement in a standing wave pattern?
Points of no displacement
What is the primary purpose of using a post-exposure bake (PEB) step in the lithography process?
To facilitate the deprotection reaction
Learn about the complex process of patterning features at critical dimensions, including the use of hard-mask layers and bottom anti-reflection coatings in VLSI fabrication. Understand the various steps involved in gate etch, resist strip, and HM removal. Quiz yourself on the intricacies of VLSI manufacturing.
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