Backside Via Etching in III-V Semiconductor Structures
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Solution Overview
Problem
The traditional process for forming back-side via holes in GaN high-electron-mobility transistors is complex, time-consuming, and costly due to the need for multiple etching and cleaning steps to prevent damage to metal layers during the formation of back-side via holes.
Innovation Solution
A semiconductor structure with a first contact metal layer, including molybdenum, tungsten, iridium, palladium, platinum, cobalt, ruthenium, osmium, or a combination thereof, is used as an etch stop layer, allowing for a higher etching rate without damaging underlying metal layers, thereby simplifying the process and reducing processing time and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple etching and cleaning steps are used to prevent damage to metal layers, then the metal layers are protected from damage, but the process becomes complex and time-consuming
Solution Approach 1:
The patent introduces a sacrificial etch stop layer (such as aluminum nitride or gallium nitride) that is deposited beforehand on the substrate before forming the metal layers. This preliminary action creates a protective barrier that simplifies subsequent processing by allowing a single etching step to define the back-side via hole without requiring multiple intermediate cleaning steps to protect the metal layers.
Solution Approach 2:
The sacrificial etch stop layer serves as an intermediary between the substrate and the metal layers. During the etching process, this intermediate layer protects the metal layers from direct exposure to the etchant, allowing the via hole to be formed through the substrate and device layers while the metal layers remain intact without requiring additional protective measures.
2Reliability
If multiple etching and cleaning steps are used to prevent damage to metal layers, then the metal layers are protected from damage, but the processing time increases
Solution Approach 1:
The sacrificial etch stop layer is deposited in advance during the device fabrication process, before the metal layers are formed. This preliminary deposition eliminates the need for multiple subsequent etching and cleaning steps, thereby reducing the total processing time while still providing adequate protection to the metal layers during via hole formation.
Solution Approach 2:
The patent merges the functions of multiple separate etching and cleaning steps into a single etching process. By using the sacrificial etch stop layer as a protective barrier, the process combines substrate removal, via hole formation, and metal layer protection into one integrated step, significantly reducing the overall processing time.
3Reliability
If multiple etching and cleaning steps are used to prevent damage to metal layers, then the metal layers are protected from damage, but the cost increases
Solution Approach 1:
The sacrificial etch stop layer is deposited during the standard device fabrication sequence, before metal layer formation. This preliminary step utilizes existing deposition equipment and processes, avoiding the need for additional specialized equipment or materials that would increase manufacturing costs, while still providing effective protection during via hole formation.
Solution Approach 2:
The patent combines multiple process steps (multiple etching steps and cleaning steps) into a single etching process enabled by the sacrificial etch stop layer. This reduction in the number of process steps decreases equipment usage time, reduces material consumption, and lowers labor costs, thereby reducing the overall manufacturing cost while maintaining metal layer protection.
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 effectively simplifies the etching process, reduces overall processing time and cost, and improves the yield, making it suitable for mass production by using the first contact metal layer as an etch stop layer during the formation of back-side via holes in III-V compound semiconductor structures.
Implementation Method 1
The first contact metal layer may serve as an etch stop layer during the formation of the back-side via hole, and thus the substrate and the III-V compound semiconductor layer may be both etched with a higher etching rate without damaging the metal layers disposed on the first contact metal layer
Data Source
AI summary
A semiconductor structure is provided. The semiconductor structure includes a substrate having a front side and a back side opposite the front side. The semiconductor structure also includes a first contact metal layer disposed on the front side of the substrate. The semiconductor structure further includes a III-V compound semiconductor layer disposed between the substrate and the first contact metal layer. Moreover, the semiconductor structure includes a via hole penetrating through the substrate and the III-V compound semiconductor layer from the back side of the substrate. The bottom of the via hole is defined by the first contact metal layer, and the first contact metal layer includes molybdenum, tungsten, iridium, palladium, platinum, cobalt, ruthenium, osmium, rhodium, rhenium, or a combination thereof.