Recessed Electrical Contacts in GaN Heterostructures
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Solution Overview
Problem
Existing methods for forming recessed electrical contacts in semiconductor heterostructures require photolithography and etching techniques, leading to surface damage, contamination, and limited flexibility in producing various types of electrical elements.
Innovation Solution
The method employs ultrashort laser pulses to form recesses in semiconductor layers without photolithography, using a protective layer and inert gas environment, allowing for controlled removal and regrowth of materials to create recessed contacts and junctions with reduced damage and increased conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If photolithography and etching techniques are used to form recessed electrical contacts, then the recesses can be formed in semiconductor layers, but surface damage and contamination occur
Solution Approach 1:
The patent replaces mechanical and chemical etching processes with laser ablation. The laser beam directly removes material through photothermal and photomechanical effects, eliminating the need for chemical etchants and mechanical contact that cause surface damage and contamination. This substitution of the material removal mechanism resolves the contradiction by achieving precise recess formation without the harmful side effects of traditional methods.
Solution Approach 2:
The patent utilizes ultrashort laser pulses with specific wavelength and duration parameters to achieve controlled material removal. By adjusting laser parameters (wavelength, pulse duration, fluence), the process achieves precise ablation without excessive heat diffusion that causes surface damage. The parameter optimization allows precise recess formation while minimizing thermal damage to surrounding areas.
2Manufacturing precision
If photolithography and masking processes are used, then recesses can be formed with specific patterns, but fabrication time and process complexity increase
Solution Approach 1:
The patent extracts and eliminates the photolithography and masking steps from the fabrication process. By using direct laser writing, the pattern definition function is integrated into the material removal step itself. The laser beam is steered to directly trace the desired pattern on the semiconductor surface, removing the need for separate pattern transfer steps and significantly reducing fabrication time while maintaining pattern accuracy.
Solution Approach 2:
The patent merges the pattern definition and material removal operations into a single laser ablation step. Instead of separate processes for patterning and etching, the laser simultaneously defines the pattern geometry and removes material in one integrated operation. This consolidation eliminates intermediate steps and reduces overall fabrication time while preserving manufacturing precision.
3Adaptability or versatility
If multiple types of recessed electrical elements are formed using traditional methods, then various electrical contacts can be created, but multiple masks and alignment processes are required
Solution Approach 1:
The patent implements a universal laser ablation process that can form different types of recessed electrical elements (ohmic contacts, Schottky contacts, recesses of varying depths and geometries) using the same equipment and basic process. By controlling laser parameters and beam positioning, the single laser system performs multiple functions that traditionally required different masks and process steps, thereby reducing device complexity while maintaining versatility.
Solution Approach 2:
The patent employs dynamic control of the laser beam parameters and positioning during the ablation process. The laser system can dynamically adjust pulse duration, fluence, and scanning speed to create different recess geometries and depths as needed. This dynamic adaptability allows formation of various electrical element types without requiring static masks for each configuration, simplifying the overall process.
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 reduces fabrication time, material consumption, and surface damage, enabling the formation of diverse electrical elements with improved conductivity and simplified technology, while avoiding toxic chemicals and alignment processes.
Implementation Method 1
forming the contact recess, reaching to the channel layer, in source and drain regions by using dry etching by inductively coupled plasma reactive ion etching (ICP-RIE) technique
Implementation Method 2
forming each said recess by directing through the transparent window in the chamber to the blank the focused ultrashort pulsed laser radiation, which has selected parameters to remove the protective layer and required thickness of the material
Data Source
Figure 1a~1b
Figure 1c~1d
Figure 1e~1f
AI summary
The invention relates to the technical field of microelectronic components and is related to the forming of recessed and regrown electrical contacts for wide-bandgap Group III nitride semiconductor components. In the regions of the heterostructure, intended for the forming of the recessed elements, each recess is formed using laser micro-processing. The top surface of the III-N semiconductor layer heterostructure, grown on the substrate is coated with at least one protective layer in order to form a blank. The blank is placed in a chamber, vacuumed or filled with an inert or shielding gas and the recess are formed separately for each contact and (or) junction and (or) electrical component. For this the focused ultrashort pulsed laser radiation is directed through the transparent window in the chamber and it is used to remove the protective layer and required thickness of the material of the heterostructure layers, forming the recess with required depth in the said heterostructure. Said blank and focused laser beam are translated in respect to each other in the controlled manner to form the next recess in the same way. The formed recess are filled with either the doped III-N semiconductor layer or (and) metal compounds, forming the recessed electrically conductive contact and (or) electrically partially conductive contact and (or) junction and (or) electrical component.