Ion-Implanted Boron Hard Masks for Deeper DRAM Capacitor Etching
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Solution Overview
Problem
Conventional boron hardmasks face limitations in selectivity during the etching of DRAM features, particularly in maintaining high aspect ratios and uniformity as device sizes shrink.
Innovation Solution
The use of boron-based hardmasks with high boron content (>90%) and ion implantation with specific ions (such as indium, helium, and neon) to enhance the etch selectivity of the hardmask relative to the underlying semiconductor structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional boron hardmasks are used for etching DRAM features, then the etching process can be performed, but the etch selectivity is insufficient leading to poor Critical Dimension Uniformity (CDU)
Solution Approach 1:
The patent changes the physical and chemical parameters of the boron hardmask by implanting ions (such as nitrogen, oxygen, or carbon ions) at specific energies and doses. This modifies the hardmask's density, composition, and etch resistance, thereby improving etch selectivity and CDU without changing the fundamental process flow
Solution Approach 2:
The patent creates a composite structure by implanting foreign ions into the boron hardmask matrix. This results in a composite material with enhanced properties, where the implanted ions create regions of varying composition that improve etch selectivity while maintaining the hardmask's structural integrity
2Reliability
If the hardmask thickness is increased to improve selectivity, then etch selectivity may improve, but the Critical Dimension Uniformity deteriorates due to thickness variations
Solution Approach 1:
Instead of changing the thickness parameter, the patent changes the compositional and physical state parameters of the hardmask through ion implantation. This allows selectivity improvement through material property modification rather than geometric parameter adjustment, thereby maintaining CDU
Solution Approach 2:
The patent transitions from adjusting selectivity in the thickness dimension to adjusting it in the compositional dimension. By implanting ions, the selectivity enhancement is achieved through chemical and physical property changes rather than increasing the physical thickness of the hardmask layer
3Reliability
If ion implantation is performed on the boron hardmask, then etch selectivity increases by at least 10%, but the process complexity increases
Solution Approach 1:
The ion implantation is performed as a preliminary step before the etching process, preparing the hardmask in advance to have enhanced selectivity. This preliminary modification ensures that the subsequent etching process proceeds with improved uniformity and selectivity without requiring complex real-time adjustments
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
The described method significantly increases the etch selectivity of the hardmask by at least 10%, allowing for deeper capacitor holes in DRAM structures without increasing the hardmask thickness, thereby improving Critical Dimension Uniformity (CDU).
Implementation Method 1
forming a plasma of all precursors within the processing region of the first semiconductor processing chamber
Implementation Method 2
implanting the boron-based hardmask with ions
Data Source
AI summary
Thicker hardmasks are typically needed for etching deeper capacitor holes in a DRAM structure. Instead of increasing the hardmask thickness, hardmasks may instead be formed with an increased etch selectivity relative to the underlying semiconductor structure. For example, boron-based hardmasks may be formed that include a relatively high percentage of boron (e.g., greater than 90%). The etch selectivity of the hardmask may be improved by performing an ion implant process using different types of ions. The ion implant may take place before or after opening the hardmask with the pattern for the DRAM capacitor holes. Some designs may also tilt the semiconductor substrate relative to the ion implant process and rotate the substrate to provide greater ion penetration throughout a depth of the openings in the hardmask.