Polysilicon Resistor Contact Sheet Resistance Reduction
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Solution Overview
Problem
The contact sheet resistance between polysilicon resistors and metal contacts in semiconductor devices is high due to the absence of a metal salicide layer on polysilicon resistors, leading to inefficient electrical connectivity.
Innovation Solution
A method is introduced where a dielectric layer is formed over a polysilicon resistor, etched to create a contact opening with overetching, followed by the formation of a metal silicide layer on the resistor, and then a metal material is filled in, with the dielectric and polysilicon portions removed to expose the silicide layer, allowing for a metal contact to be formed, thereby reducing contact sheet resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If no metal silicide layer is formed on the polysilicon resistor, then the fabrication process is simpler, but the contact sheet resistance between the polysilicon resistor and metal contact is large
Solution Approach 1:
A metal silicide layer is formed on the polysilicon resistor surface before forming the metal contact. This preliminary action of creating the silicide layer reduces the contact sheet resistance between the metal contact and polysilicon resistor, while the overall fabrication process remains integrated and efficient through subsequent selective removal steps.
2Reliability
If a metal silicide layer is formed on the polysilicon resistor, then the contact sheet resistance is reduced, but the fabrication process becomes more complex
Solution Approach 1:
The fabrication process merges the contact formation for polysilicon resistors and MOS transistors into a single integrated process. The metal silicide layer is formed simultaneously on both polysilicon resistors and S/D regions, and subsequent etching and filling operations are combined, reducing overall process complexity despite the additional silicide formation step.
Solution Approach 2:
The metal silicide layer is selectively removed from specific regions (polysilicon resistors and S/D regions) after formation, extracting it only where needed for contact formation. This selective removal allows the silicide layer to be formed universally but applied specifically, reducing contact resistance where required without affecting other areas.
3Manufacturing precision
If overetching is performed during contact opening formation, then the contact opening reaches the polysilicon resistor surface, but the dielectric layer is also etched into the polysilicon resistor
Solution Approach 1:
The overetching that removes the dielectric layer and exposes the polysilicon resistor surface is converted into a beneficial step. This selective removal of the dielectric layer creates direct access to the polysilicon resistor, enabling the subsequent formation of the metal silicide layer and metal contact with reduced contact sheet resistance.
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 the contact sheet resistance between polysilicon resistors and metal contacts, enhancing electrical connectivity and device performance.
Implementation Method 1
A metal silicide layer is formed on the polysilicon resistor in the contact opening
Data Source
AI summary
A method for fabricating a semiconductor device is described. A substrate having thereon a polysilicon resistor is provided. A dielectric layer is formed over the substrate covering the polysilicon resistor. The dielectric layer is etched to form a contact opening over the polysilicon resistor, with overetching into the polysilicon resistor. A metal silicide layer is formed on the polysilicon resistor in the contact opening. A metal material is filled in the contact opening. A portion of the dielectric layer, the metal material, and a portion of the polysilicon resistor are removed to expose the metal silicide layer. A metal contact is formed over the metal silicide layer.