Angled Ion Beam Etching for DRAM Cavity Alignment
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Solution Overview
Problem
As DRAM devices scale to smaller dimensions, the patterning of three-dimensional structures becomes increasingly challenging due to misaligned chop masks and decreasing overlay tolerance, leading to defective fin structures in semiconductor devices.
Innovation Solution
A method involving a substrate with a patterning stack, where a first pattern of linear structures is formed, followed by the creation of a mask with second linear structures at a non-zero angle. An angled ion beam is used to etch a two-dimensional array of cavities, and a tone reversal is performed to form an isolation pattern within the substrate, eliminating the need for chop masks and reducing overlay challenges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional chop mask patterning is used to form fin structures, then the process can be implemented with existing equipment, but misalignment occurs leading to defective fin structures
Solution Approach 1:
The patterning process is divided into multiple self-aligned steps: first forming mandrels, then using them as templates to create spacers, and finally using the spacers as masks for etching. This segmentation eliminates the need for separate chop mask alignment steps, as each step is automatically aligned to the previous structures through the self-aligned nature of the process.
Solution Approach 2:
Mandrel structures are formed in advance as preliminary elements that define the positions of subsequent fin structures. These mandrels serve as pre-positioned templates that guide the formation of spacers and最终的 fin structures, ensuring precise alignment without requiring separate masking steps.
2Productivity
If array pitch is reduced to increase device density, then more memory cells can be packed, but overlay tolerance decreases making patterning more difficult
Solution Approach 1:
The patterning structures serve their own alignment function without requiring external reference marks or additional masking layers. The mandrels and spacers automatically define each other's positions through conformal deposition and etching processes, making the system self-aligning and eliminating overlay tolerance requirements even at reduced pitches.
Solution Approach 2:
The invention transitions from two-dimensional planar patterning with chop masks to a three-dimensional self-aligned approach using vertically stacked mandrels and spacers. This dimensional transition allows precise lateral positioning to be achieved through vertical conformal deposition, enabling sub-50nm pitch patterning with superior alignment accuracy.
3Manufacturing precision
If angled ion beam etching is used to form elongated cavities, then precise control over cavity shape is achieved, but the process complexity increases
Solution Approach 1:
The etching process uses controlled ion beam angles and plasma chemistry parameters to achieve directional etching. By adjusting the ion beam incidence angle and etch selectivity parameters, the process forms elongated cavities with precise aspect ratios and orientations, transforming a complex shaping requirement into a controlled parameter adjustment.
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 approach enables the formation of active memory arrays with precise control over cavity elongation, improving the accuracy and reliability of semiconductor fin structures, particularly at pitches less than 50 nm, without requiring extreme ultraviolet (EUV) or other chop masks, thus enhancing the production of DRAM devices.
Implementation Method 1
directionally etching the first etch pattern using an angled ion beam, wherein a second etch pattern is formed, the second etch pattern comprising the two-dimensional array of cavities, elongated along the first direction
Data Source
AI summary
A method may include providing a substrate, comprising a patterning layer. The method may include forming a first pattern of first linear structures in the patterning layer, the first linear structures being elongated along a first direction. The method may include forming a mask over the patterning layer, the mask comprising a second pattern of second linear structures, elongated along a second direction, forming a non-zero angle with respect to the first direction. The method may include selectively removing a portion of the patterning layer while the mask is in place, wherein a first etch pattern is formed in the patterning stack, the first etch pattern comprising a two-dimensional array of cavities. The method may include directionally etching the first etch pattern using an angled ion beam, wherein a second etch pattern is formed, comprising the two-dimensional array of cavities, elongated along the first direction.