Self-Aligned Vertical Recess for 3D Stacked Channel Contacts
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Solution Overview
Problem
Current microfabrication techniques face challenges in achieving precise vertical recesses in pre-metallization dielectric (PMD) films for three-dimensional (3D) semiconductor circuits, particularly due to variability in CMP uniformity, gate cap thickness, and pattern loading effects, which hinder high-volume manufacturability.
Innovation Solution
A self-aligned method for vertical recess formation involves growing un-doped SiGe sacrificial contacts to provide etch selectivity and enable precise end-point detection during PMD film recess etching, allowing for accurate placement of cover spacers and independent processing of stacked NMOS and PMOS devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional CMP and blind recess etching methods are used for PMD film recess, then the process can be performed with standard equipment, but high variability in CMP uniformity, gate cap thickness, and pattern loading effects results in poor manufacturing precision
Solution Approach 1:
The patent introduces sacrificial contact structures as intermediary elements that mediate between the PMD film and the underlying channel structures. These sacrificial contacts serve as etch-stop layers and alignment references, enabling precise vertical recess formation without requiring complex CMP control. The sacrificial contacts are removed after serving their purpose, leaving clean interfaces for subsequent device formation.
Solution Approach 2:
The patent performs preliminary formation of sacrificial contact structures before the PMD recess etching step. These pre-formed structures provide etch selectivity and self-alignment references that guide the subsequent recess process, eliminating the need for complex real-time control during etching and reducing variability from CMP and pattern loading effects.
2Measurement precision
If self-aligned method with sacrificial contacts is used, then manufacturing precision and end-point detection are significantly improved, but the number of process steps and device complexity increase
Solution Approach 1:
The sacrificial contact structures are designed to be self-removing after serving their alignment and etch-stop functions. The removal process is simplified by using materials that are selectively removable, and the structures automatically define the recess boundaries without requiring additional measurement or control steps, reducing the net increase in process complexity.
3Ease of manufacture
If vertical recess is formed without self-alignment method, then the process is simpler with fewer steps, but variability in CMP uniformity and pattern loading effects cannot be controlled
Solution Approach 1:
The sacrificial contact structures act as intermediary reference elements that simplify the manufacturing process by providing built-in alignment guides and etch-stop layers. Rather than requiring complex control of CMP uniformity and pattern loading, the process uses these intermediaries to automatically define the recess geometry, improving reliability for high-volume manufacturing.
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 significantly reduces variability in the etch-recessed PMD process, enabling precise alignment within tight dimensional windows and enhancing the manufacturability of 3D semiconductor devices by allowing independent processing of stacked devices.
Implementation Method 1
growing un-doped SiGe sacrificial contacts to provide etch selectivity and enable precise end-point detection during PMD film recess etching
Data Source
AI summary
Aspects of the present disclosure provide a self-aligned microfabrication method, which can include providing a substrate having vertically arranged first and second channel structures, forming first and second sacrificial contacts to cover ends of the first and second channel structures, respectively, covering the first and second sacrificial contacts with a fill material, recessing the fill material such that the second sacrificial contact is at least partially uncovered while the first sacrificial contact remains covered, replacing the second sacrificial contact with a cover spacer, removing a remaining portion of the first fill material, uncovering the end of the first channel structure, forming a first source/drain (S/D) contact to cover the end of the first channel structure, covering the first S/D contact with a second fill material, uncovering the end of the second channel structure, and forming a second S/D contact at the end of the second channel structure.