Semiconductor Plug Segmentation and Selective Oxidation
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Solution Overview
Problem
As semiconductor devices become more integrated, the reduced design rules and high aspect ratios lead to a rapid decrease in process margins, making it challenging to maintain effective etch profiles and prevent undercutting during the fabrication of conductive lines and plugs.
Innovation Solution
A method involving the formation of spacers with selective oxidation to align and protect the conductive lines and plugs, ensuring the conductive line, plug head, and plug body have the same critical dimensions, and using different materials for the spacers to enhance etch control and prevent undercutting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the design rule is decreased to increase integration degree, then the integration degree is improved, but the process margin is reduced
Solution Approach 1:
The conductive plug is segmented into two distinct parts: a plug head with a first critical dimension and a plug body with a second critical dimension. This segmentation allows each part to be optimized independently for its specific function, enabling the overall structure to achieve smaller dimensions while maintaining adequate process margins for fabrication.
Solution Approach 2:
Different regions of the conductive plug are given different dimensions and properties. The plug head has a larger critical dimension to facilitate formation and alignment, while the plug body has a smaller critical dimension to achieve the required integration density. This local differentiation resolves the contradiction between small overall dimensions and manufacturability.
2Length of moving object
If the hole spacing is narrowed to miniaturize patterns, then the device size is reduced, but the etch profile is degraded
Solution Approach 1:
A spacer structure is formed in advance around the conductive line before the plug body is formed. This preliminary spacer provides a physical template that guides the subsequent etching process, ensuring that the plug body achieves the correct dimensions and position even when hole spacing is narrow. The spacer acts as a pre-established reference that maintains etch profile quality despite reduced spacing.
3Productivity
If the plug dimension is reduced to increase integration, then the device density is improved, but undercutting occurs during etching
Solution Approach 1:
The spacer structure is formed beforehand to provide a protective cushion during the etching process. This spacer extends beyond the intended final plug boundary, cushioning against over-etching and undercutting that would otherwise occur when forming small-dimension plugs. The spacer is later removed or integrated, leaving a precisely dimensioned plug without undercutting defects.
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 improves the process margin and etch profile, preventing undercutting and enhancing the electrical characteristics of semiconductor devices by maintaining precise dimensions and reducing parasitic capacitance.
Implementation Method 1
forming a second spacer by performing a selective oxidation onto a side wall of the plug body
Data Source
AI summary
A method for fabricating a semiconductor device includes: forming a first conductive layer; forming a second conductive layer over the first conductive layer; forming a conductive line by etching the second conductive layer; etching a portion of the first conductive layer to form a plug head having the same critical dimension as the conductive line; forming a first spacer that covers the conductive line and the plug head; etching the remaining first conductive layer to form a plug body that is aligned with the first spacer, wherein the plug body have a greater critical dimension than the plug head; and forming a second spacer by performing a selective oxidation onto a side wall of the plug body.