Isolation Structure Layout for Polysilicon Residue-Free Gate Removal
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Solution Overview
Problem
The scaling down of feature sizes in integrated circuit chips affects device packing density and performance due to issues with polysilicon residues during the formation of isolation structures, leading to reduced production yield.
Innovation Solution
A method involving the formation of polysilicon-on-oxide-definition edge (CPODE) structures with specific etching processes to remove excess polysilicon, ensuring complete removal of dummy poly gates and forming isolation structures to enhance production yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If feature size is scaled down to increase device packing density, then more devices can be integrated on a chip, but polysilicon residues remain during isolation structure formation, reducing production yield
Solution Approach 1:
The dummy poly gate is divided into multiple segments: a first portion that remains and a second portion that is removed. This segmentation allows selective removal of only the necessary polysilicon portion while preserving the functional gate structure, thereby eliminating residues that would otherwise reduce production yield while maintaining high device packing density
Solution Approach 2:
The second portion of the dummy poly gate is extracted and removed to form an opening that exposes the stack unit. This extraction eliminates the polysilicon residue problem in the isolation structure formation process, resolving the contradiction between maintaining high device density and ensuring clean isolation structures for high production yield
2Reliability
If isolation structures are formed using conventional methods, then device leakage is prevented, but polysilicon residues from dummy poly gates remain, affecting production yield
Solution Approach 1:
The second portion of the dummy poly gate is removed to create an opening, ensuring that no polysilicon residues remain when isolation structures are formed. This extraction maintains the leakage prevention function while eliminating the residue problem that would otherwise reduce production yield
Solution Approach 2:
By segmenting the dummy poly gate into a retained first portion and a removed second portion, the invention enables clean isolation structure formation without residues, thereby maintaining reliability for leakage prevention while improving production yield
3Reliability
If the second portion of the dummy poly gate is removed to form an opening, then polysilicon residues are eliminated, but additional manufacturing steps are required
Solution Approach 1:
The removal of the second portion of the dummy poly gate is merged with the existing isolation structure formation process. The opening created by removing the second portion is simultaneously used as the trench for the isolation structure, combining multiple functions into a single process flow and minimizing additional manufacturing steps while eliminating polysilicon residues to improve production yield
4Reliability
If the width of the second portion of the dummy poly gate is increased, then complete removal is ensured, but more material must be removed during etching
Solution Approach 1:
The dummy poly gate is designed with non-uniform width: the second portion has a greater width than the first portion, specifically engineered to ensure complete removal during etching. This local quality enhancement at the second portion ensures reliable complete removal of polysilicon residues while limiting material loss to only the necessary second portion, optimizing the balance between complete removal and material conservation
Data Source
AI summary
A method for manufacturing a semiconductor device includes: forming a dummy poly gate on a common edge of a first oxide-definition region and a second oxide-definition region, the dummy poly gate covering a stack unit, and including two first portions and a second portion disposed between the two first portions in a first direction, the first portion having a width in a second direction transverse to the first direction, the second portion having a width in the second direction, the width of the second portion being larger than the width of the first portion; forming first and second source/drain features on the first and second oxide-definition regions, respectively; removing the second portion to form a first opening that exposes the stack unit; removing the stack unit to form a second opening in spatial communication with the first opening; and forming an isolation structure in the first and second openings.