P-type Work Function Layer Prevents Contact Metal Extrusion
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Solution Overview
Problem
The integration of high-k/metal gate features in CMOS processes faces challenges due to contact metal extrusion, which affects the work function of neighboring transistors, leading to increased threshold voltage and reduced 'on' current, and causes mismatches between devices.
Innovation Solution
A P-type work function layer with good sidewall coverage is deposited around contact plugs to prevent tungsten extrusion into neighboring gate stacks, using techniques like Atomic Layer Deposition (ALD) to ensure adequate thickness and prevent contact metal from protruding into adjacent gate structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If contact metal is deposited to fill contact plugs, then electrical connectivity is achieved, but contact metal extrudes into neighboring gate stacks affecting work function
Solution Approach 1:
A barrier layer is introduced as an intermediary between the contact metal and the gate stack. This barrier layer prevents the contact metal from extruding into the gate stack while allowing the contact metal to maintain electrical connectivity to the underlying structure. The barrier layer acts as a mediator that blocks the harmful interaction between contact metal and gate dielectric/polysilicon.
Solution Approach 2:
The structure is segmented into distinct layers with the barrier layer separating the contact metal region from the gate stack region. This segmentation creates a clear boundary that prevents metal extrusion while maintaining the functional integrity of both the contact and gate structures.
2Productivity
If high-k/metal gate features are integrated in CMOS process, then device performance is improved, but contact metal extrusion causes threshold voltage increase and reduced on current
Solution Approach 1:
The barrier layer serves as a protective intermediary that prevents contact metal contamination of the high-k/metal gate structure. By blocking metal extrusion, the barrier layer preserves the precise electrical characteristics of the gate stack, including threshold voltage and on-current, enabling high-performance device operation.
3Ease of operation
If contact plugs are formed adjacent to gate structures, then interconnect functionality is achieved, but voids form during gate metal deposition allowing metal protrusion
Solution Approach 1:
The barrier layer is deposited beforehand to cushion and protect the gate structure from potential metal extrusion. This preventive measure is in place before gate metal deposition, ensuring that even if voids form during processing, the contact metal cannot protrude into the gate stack to compromise structural integrity.
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 solution effectively contains voids formed during gate metal deposition, preventing tungsten from protruding into neighboring gate stacks and maintaining the work function integrity of adjacent transistors, thereby improving device performance and yield by reducing Vcc min and maintaining 'on' current levels.
Implementation Method 1
using techniques like Atomic Layer Deposition (ALD) to ensure adequate thickness and prevent contact metal from protruding into adjacent gate structures
Data Source
AI summary
A method of preventing contact metal from protruding into neighboring gate devices to affect work functions of the neighboring gate devices is provided includes forming a gate structure. Forming the gate structure includes forming a work function layer, and forming a gate metal layer having a void, wherein the work function layer surrounds the gate metal layer. The method further includes forming a contact plug having a contact metal directly on the gate metal layer of the first gate stack, wherein the contact metal protrudes into the void, and the work function layer prevents the contact metal from protruding into a second gate stack.