Self-Aligned Contacts for Group III-V Substrates
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Solution Overview
Problem
Existing Group III-V semiconductor devices face challenges in achieving accurate lithographic registration of outer and inner contact edges as feature sizes decrease, making it difficult to maintain good Ohmic contact resistance.
Innovation Solution
A system for forming self-aligned contacts in Group III-V semiconductor substrates through electroplating a first metal contact with a straight sidewall profile, etching back the substrate to expose an emitter layer, conformally depositing a dielectric layer, and anisotropically etching to form dielectric sidewall spacers, allowing for the formation of self-aligned or doubly self-aligned second metal contacts without relying on lithographic registration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If lithographic registration is used to align contact edges, then manufacturing process is simple, but registration accuracy deteriorates as feature sizes decrease below 200 nm
Solution Approach 1:
The first metal contact structure serves as its own alignment reference for the second metal contact. The dielectric sidewall spacer is formed conformally on the first metal contact, automatically defining the position and dimensions of the second contact opening without requiring external lithographic registration. This self-aligning mechanism eliminates registration errors that plague conventional lithographic methods at sub-200 nm scales.
Solution Approach 2:
A dielectric sidewall spacer is introduced as an intermediary structure between the first and second metal contacts. This spacer acts as a physical template that transfers the dimensional information from the first contact to the second contact, enabling precise alignment through conformal deposition and anisotropic etching rather than relying on lithographic pattern transfer.
2Reliability
If contact width is reduced to maintain low Ohmic contact resistance, then contact performance improves, but lithographic registration accuracy deteriorates
Solution Approach 1:
The first metal contact structure serves as its own alignment reference for the second metal contact. The dielectric sidewall spacer is formed conformally on the first metal contact, automatically defining the position and dimensions of the second contact opening without requiring external lithographic registration. This self-aligning mechanism eliminates registration errors that plague conventional lithographic methods at sub-200 nm scales.
Solution Approach 2:
The method changes the critical dimension control parameter from lithographic resolution limits to conformal film thickness control. By using atomic layer deposition or chemical vapor deposition to form the dielectric spacer, the contact dimensions are controlled by precisely controllable thin film deposition processes rather than by lithographic patterning, enabling sub-200 nm features with high precision.
3Manufacturing precision
If self-aligned contacts are formed using dielectric sidewall spacers, then contact registration accuracy improves, but manufacturing process complexity increases
Solution Approach 1:
Multiple functions are merged into the dielectric sidewall spacer formation process. The conformal dielectric deposition simultaneously serves as an insulation layer and as an alignment template. The subsequent anisotropic etching of this spacer automatically defines both the position and dimensions of the second contact opening, combining alignment, insulation, and dimensional control functions in a single structure.
Solution Approach 2:
The first metal contact and its dielectric sidewall spacer are formed in advance as a self-aligning template before the second contact is created. This preliminary structure preparation enables the second contact to be automatically positioned with high precision, eliminating the need for complex real-time alignment procedures during subsequent processing steps.
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 precise alignment of inner and outer contact edges, improving contact registration accuracy and maintaining low Ohmic contact resistance even at sub-200 nm feature sizes, thereby enhancing the performance of devices like HBTs and HEMTs.
Implementation Method 1
electroplating a first metal contact onto a Group III-V semiconductor substrate
Implementation Method 2
conformally depositing a dielectric layer on a vertical side of the first metal contact, the emitter semiconductor layer and the semiconductor substrate
Implementation Method 3
anisotropically etching the dielectric off of the semiconductor substrate to form a dielectric sidewall spacer on the vertical side of the first metal contact
Data Source
AI summary
A system for forming self-aligned contacts includes electroplating a first metal contact onto a Group III-V semiconductor substrate, the first metal contact having a greater height than width and having a straight sidewall profile, etching back the semiconductor substrate down to a base layer to expose an emitter semiconductor layer under the first metal contact, conformally depositing a dielectric layer on a vertical side of the first metal contact, a vertical side of the emitter semiconductor layer and on the base layer, anisotropically etching the dielectric layer off of the semiconductor substrate to form a dielectric sidewall spacer on the vertical side of the first metal contact and providing a second metal contact immediately adjacent the dielectric sidewall spacer.