Semiconductor Recess Etching Using Boron Deposition
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In the fabrication of semiconductor devices, particularly cylindrical capacitors, the use of chlorine (Cl2) for dry etching leads to inadequate selective removal of titanium nitride films, resulting in undesired etching of the sidewall portion adjacent to the opening, which reduces the lower electrode's capacitance below the designed value due to the micro-loading effect and high reactivity of chlorine ions.
Innovation Solution
Employing a boron compound as an etching gas during dry etching to form a deposition film that preferentially covers the top surface of the interlayer insulating film, allowing selective removal of the conductive film from the top surface while preserving the film on the bottom and sidewall of the recess, thereby reducing etching of the sidewall portion and maintaining sufficient film thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If chlorine (Cl2) is used for dry etching to remove titanium nitride film, then adequate etching rate and selective ratio are achieved, but the sidewall portion adjacent to the opening is undesirably etched due to micro-loading effect and high reactivity, reducing lower electrode capacitance
Solution Approach 1:
A protective film is formed in advance within the recess (hole) before the dry etching process. This preliminary protective layer prevents the conductive film on the sidewall and bottom from being etched, while allowing the conductive film on the interlayer insulating film surface to be removed. The protective film is subsequently removed after the selective removal is complete.
Solution Approach 2:
The protective film acts as an intermediary element that temporarily protects the conductive film in the recess during the dry etching process. It mediates between the etching gas and the conductive film, allowing selective removal of the conductive film on the interlayer insulating film while preserving the conductive film on the sidewall and bottom of the recess.
2Reliability
If a protective insulating film is formed in the capacitor hole before dry etching, then the bottom of the hole is protected from etching, but the process complexity increases and fabrication cost rises
Solution Approach 1:
The etching process itself is utilized to form the protective film through deposition during the etching operation. Rather than requiring a separate protective film formation process, the protective film is generated in-situ during the dry etching process, thereby reducing overall process complexity while maintaining the protective function.
Solution Approach 2:
The protective film formation and the selective removal process are merged into a single integrated process step. The protective film is formed and the selective removal is performed in one continuous operation, eliminating the need for separate protective film formation and removal steps, thereby reducing process complexity.
3Manufacturing precision
If the conductive film is completely removed from the interlayer insulating film surface, then the lower electrode capacitance is maximized, but connection to the contact plug is lost if the bottom of the hole is etched
Solution Approach 1:
The protective film is selectively positioned only within the recess (hole) structure, providing localized protection to the conductive film on the sidewall and bottom. This local protection allows the conductive film on the interlayer insulating film surface to be completely removed for maximizing capacitance, while the conductive film in the recess remains protected to maintain contact plug connection.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method effectively restricts etching on the sidewall surface adjacent to the opening, ensuring the conductive film's thickness on the sidewall and bottom of the recess is maintained, enhancing the product yield and achieving the desired capacitance, as demonstrated by SEM photographs showing complete closure of the hole opening and sufficient film thickness on the sidewall and bottom.
Implementation Method 1
Employing a boron compound as an etching gas during dry etching to form a deposition film that preferentially covers the top surface of the interlayer insulating film
Implementation Method 2
selective removal of the conductive film from the top surface while preserving the film on the bottom and sidewall of the recess
Data Source
AI summary
A conductive film is formed to extend from a bottom and a sidewall of a recess formed in an interlayer insulating film onto a top surface of the interlayer insulating film. Dry etching of the conductive film is performed such that a portion of the conductive film remains on the bottom and sidewall of the recess. The dry etching is also performed such that a deposition film is formed on a top portion of the recess.