Tilt-Implanted Mask for Recess Alignment in Semiconductor Fabrication
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Solution Overview
Problem
Conventional methods for forming recesses in semiconductor structures, particularly for vertical transistors, face challenges in precise alignment control as feature sizes shrink below 100 nm, leading to misalignment issues and reduced yield due to overlay errors in photolithography.
Innovation Solution
A method involving the use of protrusions with tilt-implanted mask layers to form a recess, where a patterned mask layer is created by alternating implanting masks adjacent to the side walls of the protrusions, allowing for precise control of the recess location between trench capacitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If photolithography methods are used to define the recess, then the fabrication process is simple and straightforward, but the alignment precision deteriorates due to overlay errors during exposure
Solution Approach 1:
The patent introduces an intermediary self-aligned process using tilt-implantation to transfer the recess pattern from the photoresist layer to the mandrel structure. This intermediary step acts as a mediator that converts the low-precision photolithography pattern into a high-precision recess definition, eliminating the direct reliance on photolithography alignment while maintaining process simplicity
Solution Approach 2:
The patent performs preliminary actions by forming the photoresist pattern first, then using it as a template for subsequent self-aligned tilt-implantation. The photoresist pattern is not directly used for etching but serves as a preliminary guide that is later replaced by the self-aligned implantation process, which achieves the final precise recess definition
2Productivity
If feature size is reduced to below 100 nm to increase integration density, then more memory cells can be packed on the chip, but the alignment control becomes more difficult and overlay errors increase
Solution Approach 1:
The patent transitions from two-dimensional planar photolithography alignment to three-dimensional self-aligned tilt-implantation. By utilizing the vertical dimension and angular implantation, the process achieves precise lateral alignment without relying on planar overlay control, enabling sub-100 nm feature scaling while maintaining alignment precision
Solution Approach 2:
The patent implements a self-aligned process where the implantation masks are automatically positioned by the protrusions themselves, without requiring additional alignment steps. The protrusions serve as self-generated alignment references that guide the tilt-implantation process, eliminating the need for external alignment control and enabling precise sub-100 nm recess formation
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 enables precise alignment and formation of recesses, improving the yield of semiconductor fabrication by reducing overlay errors and ensuring accurate placement of a recessed gate relative to deep trenches.
Implementation Method 1
The mask layer is then tilt-implanted using a first implanting mask adjacent to the first side wall of the protrusions. The mask layer is then tilt-implanted again using a second implanting mask adjacent to the second side wall of the protrusions.
Data Source
AI summary
A method for forming a recess. The method includes providing a substrate with two protrusions having a first side wall and a second side wall opposite to the first side wall disposed above the substrate, conformally forming a mask layer on the substrate and the protrusions, tilt implanting the mask layer using a first implanting mask adjacent to the first side wall of the protrusions, removing implanted portions of the mask layer to form a patterned mask layer, and etching the substrate using the patterned mask layer, thereby forming a recess.