Polysilicon Resistor Implant Angles for Tempco Uniformity
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Solution Overview
Problem
Resistors in integrated circuits fabricated using advanced technology nodes suffer from increased variability in resistance and temperature coefficient due to limitations in lithography/etch/implant processes and dopant loss, impacting circuit functionality and yield.
Innovation Solution
Varying the angle and/or energy level of ion implantation during the manufacturing process to achieve a more uniform temperature coefficient of resistance across a wafer and between wafers, using non-zero-degree angle ion implantation to compensate for dopant loss in narrower lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional ion implantation processes are used, then manufacturing simplicity is maintained, but resistance and temperature coefficient variability increases due to dopant loss in narrower lines
Solution Approach 1:
The patent applies local quality by implementing different ion implantation angles for different linewidth regions. Specifically, first ion implantation is performed at a first angle for first linewidths and at a second angle for second linewidths, where the angles differ to compensate for dopant loss variations across different line widths. This localized differentiation resolves the contradiction by improving uniformity precisely where needed without unnecessarily complicating the entire manufacturing process.
Solution Approach 2:
The patent employs parameter changes by varying the ion implantation angle as a critical process parameter. The method uses different implantation angles (first angle vs. second angle) to control dopant distribution in different linewidth regions. This parameter modification enables compensation for dopant loss without requiring fundamental changes to the implantation equipment or process architecture, thus improving precision while limiting complexity increase.
2Productivity
If advanced technology nodes are used, then circuit integration density is improved, but resistance variability increases due to lithography/etch/implant process limitations
Solution Approach 1:
The patent addresses the precision issue in advanced technology nodes by applying local quality through region-specific ion implantation angles. The method differentiates between first and second linewidths, applying optimized implantation angles to each region to compensate for process limitations. This localized approach enables advanced integration density while maintaining resistance uniformity by tailoring the implantation process to specific geometric requirements.
Solution Approach 2:
The patent implements preliminary action by performing ion implantation with optimized angles before subsequent processing steps that could cause dopant loss. The method proactively compensates for expected dopant loss during lithography, etch, and implant processes by adjusting the implantation parameters in advance. This preliminary optimization enables advanced technology nodes to achieve both high integration density and acceptable resistance uniformity.
3Manufacturing precision
If dopant loss is reduced through process optimization, then resistance uniformity is improved, but manufacturing process complexity increases
Solution Approach 1:
The patent balances dopant distribution uniformity with manufacturing simplicity by applying local quality only where necessary. The method uses different ion implantation angles for first and second linewidths, focusing the complexity on specific regions where dopant loss occurs. This targeted approach improves dopant distribution uniformity without requiring complete process re-engineering, thereby maintaining reasonable ease of manufacture.
Solution Approach 2:
The patent applies partial action by implementing angle differentiation only for specific linewidth regions rather than uniformly across all structures. The method performs first ion implantation at a first angle for first linewidths and at a second angle for second linewidths, applying the more complex approach only where needed to compensate for dopant loss. This partial application reduces the overall manufacturing complexity while still achieving improved dopant distribution uniformity.
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
Reduces variability in resistance and temperature coefficient, improving circuit performance and yield by ensuring uniform dopant distribution across different linewidths.
Implementation Method 1
a first ion implantation step that introduces a first dopant into the polysilicon resistor body
Data Source
AI summary
Methods and semiconductor circuits are described in which a polysilicon resistor body is formed over a semiconductor substrate. A first dopant species is implanted into the polysilicon resistor body at a first angle about parallel to a surface normal of a topmost surface of the polysilicon resistor body. A second dopant species is implanted into the polysilicon resistor body at a second angle greater than about 10° relative to the surface normal. The combination of implants reduces the different between the temperature coefficient (tempco) of resistance of narrow resistors relative to the tempco of wide resistors, and brings the tempco of the resistors closer to a preferred value of zero.