Nitride Semiconductor Cap Layer Cracking Prevention
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Solution Overview
Problem
The formation of an effective AlN cap layer on an n-GaN layer is challenging due to surface roughening after ion implantation, making it difficult to achieve sufficient thickness and control ion implantation through a two-layer laminated cap layer.
Innovation Solution
A method involving the formation of a laminated body with a first nitride semiconductor layer, a second nitride semiconductor layer, and a third nitride semiconductor layer, where a partial region of the third layer is removed to expose the second layer, allowing ion implantation and subsequent annealing, with the second and third layers being epitaxially grown to prevent cracking and ensure adequate cap layer thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cap layer is formed on the n-GaN layer after ion implantation, then the cap layer can protect the substrate during annealing, but the surface roughening after ion implantation makes it difficult to form an AlN layer with sufficient thickness
Solution Approach 1:
The cap layer is divided into multiple layers with different materials and functions: a first cap layer (AlN) for protection, a second cap layer (AlGaN) for controlling ion implantation, and a third cap layer (GaN) for structural support. This segmentation allows each layer to optimize its specific function while working together as a unified protective structure.
Solution Approach 2:
The invention uses a composite cap layer structure combining AlN, AlGaN, and GaN layers. Each material contributes different properties: AlN provides excellent protection and lattice matching, AlGaN offers controllable ion implantation characteristics, and GaN provides structural stability. The composite structure resolves the contradiction by integrating multiple material advantages.
2Strength
If a two-layer laminated body of AlN and GaN is formed as a cap layer, then the cap layer can prevent substrate breaking, but it is difficult to control the ion implantation through the cap layer
Solution Approach 1:
The AlGaN layer serves as an intermediary between the AlN protection layer and the GaN structural layer. It mediates the ion implantation process by providing a controllable barrier that allows precise control over ion penetration depth and distribution, while the outer AlN layer continues to provide protection against substrate breaking.
Solution Approach 2:
The cap layer structure implements local quality by having different layers with different properties at different positions. The AlN layer provides maximum protection, the AlGaN layer provides controlled ion interaction, and the GaN layer provides structural support. Each layer's properties are optimized for its specific location and function in the overall structure.
3Reliability
If the third nitride semiconductor layer is made thicker to ensure cap layer effectiveness, then the protection function is improved, but the ion implantation control becomes more difficult
Solution Approach 1:
The protective function is segmented across three layers rather than concentrated in one thick layer. The first AlN layer (5-20 nm) and third GaN layer (20-100 nm) provide protection, while the intermediate AlGaN layer (10-50 nm) controls ion implantation. This segmentation allows the total thickness to be distributed optimally for both protection and control functions.
Solution Approach 2:
The invention changes the compositional parameter of the intermediate layer by using AlGaN with adjustable aluminum content. By varying the Al composition ratio, the ion implantation characteristics can be precisely tuned while maintaining adequate protection. This parameter adjustment allows independent optimization of protection thickness and ion implantation control without direct trade-off.
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 the formation of a stable AlN cap layer, preventing cracking and allowing for controlled ion implantation and annealing, thereby improving the manufacturing process for nitride semiconductor devices.
Implementation Method 1
the second nitride semiconductor layer and the third nitride semiconductor layer are epitaxially grown on the first nitride semiconductor layer in this order
Implementation Method 2
implanting ions to the first nitride semiconductor layer from the partial region where the third nitride semiconductor layer is removed at least through the second nitride semiconductor layer
Implementation Method 3
annealing the first laminated body
Data Source
AI summary
A method of manufacturing a nitride semiconductor device is provided, comprising: forming, on a substrate, a first laminated body where a first nitride semiconductor layer, a second nitride semiconductor layer and a third nitride semiconductor layer are laminated in this order; subsequent to the forming, removing a partial region of the third nitride semiconductor layer, subsequent to the removing; implanting ions to the first nitride semiconductor layer from the partial region where the third nitride semiconductor layer is removed at least through the second nitride semiconductor layer; and subsequent to the implanting the ions, annealing the first laminated body.