Y-Shape Metal Gate Transistor for Depletion Avoidance
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Solution Overview
Problem
Current metal-oxide-semiconductor field-effect transistors (MOSFETs) face issues with poly-silicon gate depletion, leading to reduced gate capacitance and impaired current speed due to boron penetration and poor step coverage of barrier layers in recesses during metal gate formation in advanced semiconductor manufacturing.
Innovation Solution
A Y-shaped metal gate structure is introduced, where a bevel edge is formed around the spacer to create a wider recess opening, allowing for better barrier layer step coverage and void-free metal gate formation, using a method that includes forming a substrate with a gate temporary layer, doping regions, and sequential deposition of insulating, dielectric, and conductive layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal gate is formed in a recess with high depth/width ratio, then the depletion effect is avoided, but the barrier layer forms poor step coverage and causes overhang effect
Solution Approach 1:
The patent introduces a bevel edge structure that modifies the geometry of the recess from a simple vertical cylinder to a shape with an inclined upper portion. This dimensional change in the recess profile allows the barrier layer to be deposited with proper step coverage on the bevel edge, preventing overhang formation while still maintaining the necessary recess depth for depletion effect avoidance.
2Manufacturing precision
If the recess opening is made smaller due to overhang formation, then the barrier layer coverage is improved, but voids form during metal filling
Solution Approach 1:
The bevel edge structure is formed as a preliminary action before barrier layer deposition and metal filling. This pre-formed bevel edge provides a proper geometric foundation that ensures both good barrier layer step coverage and adequate metal filling without voids, preventing the need for corrective actions later in the process.
3Ease of manufacture
If poly-silicon gate is used, then the manufacturing process is simpler, but carrier depletion occurs reducing gate capacitance
Solution Approach 1:
The patent extracts the problematic poly-silicon material from the gate structure and replaces it with a metal gate. By removing the poly-silicon gate that causes depletion effect, the invention achieves high gate capacitance while maintaining manufacturing feasibility through the replacement metal gate approach with bevel edge structure.
Data Source
AI summary
A metal oxide semiconductor (MOS) transistor with a Y structure metal gate is provided. The MOS transistor includes a substrate, a Y structure metal gate positioned on the substrate, two doping regions disposed in the substrate on two sides of the Y structure metal structure, a spacer, an insulating layer positioned outside the spacer, a dielectric layer positioned outside the insulating layer and a bevel edge covering the spacer. The spacer has a vertical sidewall, and the vertical sidewall surrounds a recess. A part of the Y structure metal gate is disposed in the recess, and a part of the Y structure metal gate is positioned on the bevel edge.