Ion Implantation Amorphized Barrier Layer for HEMT Source Drain Etch Control
Solution Overview
Problem
High electron mobility transistors (HEMTs) face challenges in achieving precise and uniform etch depths for source and drain contacts due to the lack of an etch stop layer and time-dependent etching, leading to inconsistent contact resistance and roughness in the recessed regions.
Innovation Solution
The method involves using ion implantation to amorphize a portion of the barrier layer, which significantly increases the etch rate of that portion, allowing for precise control of the recessed region depth and reducing roughness, using either wet or dry etching processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching is used to create recessed regions in the barrier layer, then the etch process can be performed, but the etch depth cannot be precisely controlled due to lack of etch stop layer and time-dependent etching
Solution Approach 1:
Ion implantation is performed before the etching process to amorphize the barrier layer at the desired recess depth. This preliminary action creates a distinct amorphized region that serves as an effective etch stop, allowing precise depth control without requiring a separate etch stop layer.
Solution Approach 2:
The physical and chemical properties of the barrier layer are changed through ion implantation, transforming the crystalline structure into an amorphous state at the target depth. This parameter change creates a clear distinction between etched and unetched regions, enabling precise depth control.
2Reliability
If etching is performed to reduce bulk resistance through the barrier layer, then contact resistance is reduced, but depth non-uniformity occurs due to time dependent etching
Solution Approach 1:
Ion implantation creates a localized amorphized region with distinct properties from the surrounding crystalline barrier layer. The etching process then selectively removes material from the amorphized region, ensuring uniform depth across the contact area while maintaining precise depth control.
Solution Approach 2:
The barrier layer is pre-modified through ion implantation to create an amorphized zone at the desired recess depth. This preliminary modification ensures that subsequent etching proceeds uniformly to the exact desired depth, eliminating depth non-uniformity issues.
3Reliability
If the etch process is extended to achieve deeper recesses, then bulk resistance is reduced, but roughness of the recessed region increases
Solution Approach 1:
Ion implantation changes the physical state of the barrier layer material at the target depth, creating an amorphous phase that etches more cleanly and uniformly. This parameter change allows deeper recesses to be formed with reduced surface roughness compared to conventional etching.
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 enables consistent and repeatable reduction in contact resistance and improves the uniformity of the recessed region, achieving lower contact resistance and smoother surfaces for HEMT fabrication.
Implementation Method 1
using an ion implantation process to amorphize a portion of the barrier layer up to a specific depth
Implementation Method 2
The etch rate of this amorphized portion is much faster than that of the rest of the barrier layer
Data Source
AI summary
A method of fabricating a high electron mobility transistor is disclosed. The method comprises using an ion implantation process to amorphize a portion of the barrier layer to a specific depth. The etch rate of this amorphized portion is much faster than that of the rest of the barrier layer. In this way, the depth of the recessed regions into which the source and drain contacts are disposed is more tightly controlled. Further, the etching process may be a wet or dry etch process. The roughness of the recessed region may also be improved using this approach.