Self-Aligned Contact Plugs for Semiconductor Subsurface Structures
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Solution Overview
Problem
Existing semiconductor devices with subsurface structures face challenges in reducing the distance between neighboring structures reliably, as conventional mask lithography methods limit the alignment precision for contact openings, hindering carrier confinement effects.
Innovation Solution
The method involves growing semiconductor oxide pillars on semiconductor mesas, filling the spaces between them with auxiliary materials to form alignment plugs, and selectively removing the oxide pillars to create contact spacers and plugs that directly adjoin the mesas, allowing for self-aligned contact formation without additional lithographic masks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional mask lithography is used for contact openings, then alignment between contact openings and subsurface structures can be achieved, but the minimum distance between neighboring subsurface structures cannot be reduced further due to alignment tolerance limitations
Solution Approach 1:
The contact openings are formed using a self-aligned process where the contact opening mask is aligned to the subsurface structures through their mutual geometric relationship rather than requiring separate alignment steps. The contact openings are defined by the intersection of the contact opening mask and the projected shadow of the subsurface structures, eliminating the need for additional alignment tolerance margins
Solution Approach 2:
The patent transitions from planar 2D mask alignment to a 3D self-aligned approach where the contact openings are defined by the vertical projection of subsurface structures onto the contact opening plane. This dimensional transition allows the contact openings to be automatically positioned relative to the subsurface structures without requiring lateral alignment tolerances
2Reliability
If the distance between neighboring subsurface structures is reduced to exploit carrier confinement effects, then device performance is improved, but alignment reliability deteriorates with conventional lithography methods
Solution Approach 1:
The self-aligned contact formation process eliminates alignment errors by using the subsurface structures themselves as the reference for contact opening positioning. The contact openings are automatically centered on the subsurface structures through the geometric projection relationship, ensuring reliable alignment even at reduced distances between structures
Solution Approach 2:
The patent performs preliminary formation of the subsurface structures first, which then serve as the template for subsequent contact opening formation. This preliminary action establishes the reference geometry that automatically defines the contact opening positions, ensuring alignment reliability before the contact openings are created
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 further reduction of distances between subsurface structures to less than 300 nm, enhancing semiconductor device performance by reducing process inhomogeneities and improving carrier confinement, leading to lower device parameter deviations among semiconductor devices.
Implementation Method 1
Semiconductor oxide pillars are selectively grown on semiconductor mesas between precursor structures
Data Source
AI summary
A semiconductor device includes subsurface structures extending from a main surface into a semiconductor portion, each subsurface structure including a gate electrode dielectrically insulated from the semiconductor portion. The semiconductor device further includes alignment plugs in a vertical projection of the subsurface structures, contact spacers extending along sidewalls of the alignment plugs tilted to the main surface, and contact plugs directly adjoining semiconductor mesas between the subsurface structures. The contact plugs are provided between opposing ones of the contact spacers.