HKMG Contact Resistance Reduction via Wet Etching
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Solution Overview
Problem
Conventional semiconductor devices exhibit high contact resistance between the contact member and the metal gate, with significant variations across different devices, due to the limitations of dry etching processes in forming uniform contact holes.
Innovation Solution
A semiconductor device manufacturing method involving a wet etching process with a specific etchant composition and duration to form a second contact hole larger than the first, reducing contact resistance by increasing the contact surface area, and a semiconductor device structure with a contact member having distinct regions to enhance electrical contact with the metal gate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional dry etching process is used to form contact holes, then the manufacturing process is simple and fast, but the contact resistance between the contact member and the metal gate is relatively large with significant variations
Solution Approach 1:
The etching process is divided into two distinct stages: first, a dry etching process forms an initial contact hole through the interlayer dielectric layer; second, a wet etching process enlarges the contact hole to increase the contact surface area with the metal gate. This segmentation allows each process to optimize for its specific function, reducing overall contact resistance while maintaining manufacturing efficiency.
Solution Approach 2:
A barrier layer is introduced as an intermediary element between the metal gate and the contact member. This barrier layer serves multiple functions: it provides a suitable surface for the contact member to adhere to, reduces contact resistance, and prevents unwanted diffusion. The barrier layer acts as a mediator that improves the electrical interface without requiring direct contact between the metal gate and contact member.
2Reliability
If the contact hole size is increased to reduce contact resistance, then the contact resistance decreases, but the manufacturing precision and uniformity across wafer lots become more difficult to control
Solution Approach 1:
The contact hole formation is segmented into two processes with distinct purposes: the dry etching process creates a precisely controlled initial hole with defined dimensions and shape, while the wet etching process uniformly enlarges the hole across the entire wafer. This segmentation allows the precision-critical step to be performed by the more controllable dry etching process, while the wet etching provides uniform enlargement without compromising precision.
Solution Approach 2:
The etching parameters are changed between the two processes: the dry etching uses plasma-based chemistry with controlled ion bombardment for precise anisotropic etching, while the wet etching uses liquid chemistry for isotropic enlargement. By changing the etching medium and parameters between steps, the process achieves both precision and uniformity in the final contact hole dimensions.
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 method significantly reduces contact resistance and variations across different devices by ensuring a larger contact surface area and uniformity in contact hole sizes, improving the electrical performance of semiconductor devices.
Implementation Method 1
removing a portion of the metal gate using a wet etching process to form a second contact hole having a cross-sectional size larger than a cross-sectional size of the first contact hole
Data Source
AI summary
A method of manufacturing a semiconductor device includes providing a substrate, forming a gate structure including a metal gate on the substrate, forming an interlayer dielectric layer on the gate structure, forming a first contact hole extending through the interlayer dielectric layer to expose a surface of the metal gate, and removing a portion of the metal gate using a wet etching process to form a second contact hole having a cross-sectional size larger than a cross-sectional size of the first contact hole.