Nitride Semiconductor Gate Structure With Spacer-Defined Short Channel
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Solution Overview
Problem
Existing semiconductor devices face challenges in reducing channel length without relying on expensive photolithographic equipment, leading to increased manufacturing costs and complex exposure and etching processes.
Innovation Solution
A novel gate structure is introduced, comprising an outer and inner spacer that collaboratively form a gate trench with a wider bottom portion, allowing for reduced gate length without expensive equipment, and includes a gate electrode separated by spacers for improved insulation and reduced leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional photolithographic methods are used to reduce channel length, then manufacturing precision is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The gate structure is segmented into multiple components: outer spacers, inner spacers, and a gate electrode. The outer spacers define the gate trench, while inner spacers are formed within the trench to create a multi-level structure. This segmentation allows precise control of channel length through spacer thickness rather than requiring complex photolithographic patterning.
Solution Approach 2:
Spacers serve as intermediary structures that mediate between the photolithographic patterning step and the final gate formation. The outer spacers act as templates that define the gate trench dimensions, while inner spacers further refine the channel length. This intermediary approach replaces direct photolithographic channel length definition with a multi-step spacer-based method.
2Speed
If gate length is reduced to improve frequency performance, then current gain cutoff frequency is improved, but gate leakage increases
Solution Approach 1:
The gate structure transitions from a planar configuration to a three-dimensional multi-level structure with outer spacers, inner spacers, and a gate electrode at different vertical levels. This dimensional change allows the gate length to be reduced for improved frequency performance while the vertical spacer structures provide additional insulation paths that suppress gate leakage.
Solution Approach 2:
The gate structure employs composite material arrangements with different spacer materials and a gate electrode material. The spacers provide electrical insulation while the gate electrode provides conductivity. This composite structure enables reduced gate length for higher frequency operation while maintaining low gate leakage through the insulating spacer layers.
3Ease of manufacture
If simple spacer-based gate formation is used to reduce manufacturing cost, then ease of manufacture is improved, but gate structure precision may be compromised
Solution Approach 1:
The outer spacers are formed in advance to define the gate trench dimensions before the actual gate electrode formation. This preliminary action establishes precise dimensional boundaries that guide subsequent processing steps. The inner spacers are also formed preliminarily within the trench to pre-establish the channel length, eliminating the need for complex real-time patterning adjustments.
Solution Approach 2:
The gate structure dimensions are controlled by changing the thickness parameters of the outer and inner spacers rather than relying on complex photolithographic patterning parameters. By controlling spacer thickness through deposition process parameters, the gate structure dimensions are precisely defined in a simpler and more cost-effective manner.
Data Source
AI summary
A semiconductor device includes a first and a second nitride-based semiconductor layers and a gate structure. The gate structure includes an outer spacer, an inner spacer and a gate electrode. The outer spacer has at least two opposite inner sidewalls to define a gate trench. The inner spacer is within the gate trench. The gate electrode disposed in the gate trench and covered by the inner spacer, wherein the inner spacer and the gate electrode extend downward to collaboratively form a bottom portion of the gate structure with a first width greater than a second width of a bottom surface of the gate electrode.