Self-Aligned Mesa Spacer for LED Alignment Precision
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Solution Overview
Problem
The photolithographic process for fabricating LEDs often results in misalignment of features, leading to decreased optical performance due to the need for precise alignment of mask templates with reference points, which can be error-prone and cause off-centered electrical contacts.
Innovation Solution
A self-alignment technique is employed where a spacer is formed around the electrical contact, acting as a hard mask during etching to form a mesa structure, ensuring the contact is centered and eliminating the need for additional photolithography steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If photolithography with mask templates is used to pattern semiconductor layers, then features can be defined, but misalignment occurs between features leading to decreased optical performance
Solution Approach 1:
The electrical contact is formed first as a reference feature, and the spacer is deposited around it before the mesa etch. This preliminary formation of the contact and spacer ensures that subsequent features are automatically aligned to the contact, eliminating alignment errors that would occur with traditional photolithography sequencing.
Solution Approach 2:
The spacer formed around the electrical contact serves a dual function: it defines the mesa boundary and automatically ensures the contact is centered within the mesa. The structure self-aligns the contact position without requiring additional alignment steps or reference marks, making the system self-correcting for alignment errors.
2Manufacturing precision
If additional photolithography steps are used to define mesa shape, then alignment can be controlled, but process complexity increases
Solution Approach 1:
The spacer serves multiple functions simultaneously: it acts as an etch mask to define the mesa boundary, provides a reference for contact centering, and eliminates the need for separate photolithography steps to define the mesa shape. This multi-functionality reduces overall process complexity while maintaining precision.
Solution Approach 2:
The formation of the mesa boundary and the alignment reference are merged into a single spacer structure. Instead of using separate photolithography steps to define both the mesa shape and ensure contact alignment, the spacer combines both functions, reducing the number of process steps required.
3Manufacturing precision
If photolithography alignment is used, then features can be positioned, but misalignment errors occur causing off-centered contacts
Solution Approach 1:
The spacer formed around the electrical contact automatically ensures the contact is centered within the mesa by providing a physical reference that is inherently aligned to the contact. This self-aligning mechanism eliminates measurement and alignment errors that would occur with photolithography, as the spacer's position is directly determined by the contact's position.
Solution Approach 2:
The spacer is formed asymmetrically around the contact in the sense that it is deposited conformally on all sides of the contact, creating a symmetric spacer structure that inherently centers the contact. This geometric relationship ensures that regardless of contact position variations, the contact remains centered within the mesa defined by the spacer outer edge.
Data Source
AI summary
Described are light emitting apparatus with self-aligned elements and techniques for manufacturing such light emitting apparatus. In certain embodiments, a method for manufacturing a light emitting apparatus involves forming a plurality of semiconductor layers including a first semiconductor layer, a second semiconductor layer, and a light emission layer between the first semiconductor layer and the second semiconductor layer. The method further involves forming an electrical contact and a spacer. The electrical contact is formed on a surface of the first semiconductor layer. The spacer is formed on the surface of the first semiconductor layer, around the electrical contact. After forming the spacer, the plurality of semiconductor layers is etched to form a mesa with sidewalls that extend from an outer edge of the spacer. The spacer operates as an etch mask that causes the electrical contact to be substantially centered between opposing sidewalls of the mesa.