Tilted Implant Poly Resistor for Dimension Insensitive Resistance
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Solution Overview
Problem
Conventional semiconductor manufacturing processes struggle to produce polycrystalline silicon resistors with high sheet resistances and low tolerance, as their resistance is highly dependent on variations in critical dimensions.
Innovation Solution
A method involving the formation of a dielectric layer and a polycrystalline silicon layer, followed by a tilted implantation process that dopes the sidewalls of the poly layer, creating a lateral doping profile with peaks near the edges and a trough in the middle, allowing the resistor to be insensitive to critical dimension variations, and simultaneously forming a drain and source of a transistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional doping methods are used to form poly resistors, then the manufacturing process is simple, but the resistance tolerance is poor due to high dependence on critical dimension variations
Solution Approach 1:
The patent applies tilted implantation to introduce dopants along the sidewalls of the poly layer, adding a vertical/dimensional aspect to the doping process. This sidewall doping creates a lateral doping profile that compensates for critical dimension variations, thereby improving resistance tolerance without significantly complicating the manufacturing process
Solution Approach 2:
The patent implements non-uniform doping by concentrating dopants at the sidewalls and edges of the poly layer through tilted implantation. This creates localized high-doping regions that form a compensating lateral profile, making the overall resistance insensitive to critical dimension variations while maintaining simple manufacturing
2Manufacturing precision
If tilted implantation is used to dope sidewalls for critical dimension insensitivity, then resistance tolerance improves, but the manufacturing process becomes more complex
Solution Approach 1:
The patent combines the poly resistor formation and transistor source/drain formation into a single tilted implantation step. This merging of operations achieves multiple objectives simultaneously: creating sidewall doping for resistance tolerance, forming lateral doping profiles for critical dimension insensitivity, and doping the substrate for source and drain regions, thereby simplifying the overall manufacturing process despite the complexity of tilted implantation
3Reliability
If conventional doping is used, then the manufacturing process is straightforward, but poly resistors cannot achieve very low tolerance requirements
Solution Approach 1:
The patent uses tilted implantation to dope along the sidewalls of the poly layer, introducing a vertical dimension to the doping process. This creates a lateral doping profile with peaks near edges and trough in the middle, which compensates for critical dimension variations and achieves very low resistance tolerance
Solution Approach 2:
The patent changes the implantation parameters by using a tilted angle instead of perpendicular implantation. This parameter change enables dopants to reach the sidewalls and create the desired lateral doping profile, achieving high reliability with very low tolerance while managing process complexity
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
The tilted implantation method ensures that the resistance of the poly resistor is determined by the doping dose, making it insensitive to variations in critical dimensions, and allows for the simultaneous formation of a transistor's drain and source, enhancing manufacturing process reliability.
Implementation Method 1
a tilted implant may be used to dope the sidewalls of the poly layer
Data Source
AI summary
A semiconductor device having a substrate, a dielectric layer, a polycrystalline silicon (“poly”) resistor, a drain, and a source is disclosed. After implantation, the poly resistor may have a lateral doping profile with two peaks, one near each edge of the poly resistor, and a trough near the middle of the poly resistor. Such a doping profile can allow the poly resistor to have a resistance that is insensitive to small variations in critical dimension of the poly resistor. The resistance of the poly resistor may be determined by the doping dose of the tilted implant used to form the poly resistor. The tilted implant may be used to form the drain and the source of a transistor substantially simultaneously as forming the poly resistor.