Copper Hybrid Bonding Structure for Low-Temperature Interconnects
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Solution Overview
Problem
Copper-based microelectronic elements face challenges such as difficulty in dry etching, high diffusivity, poor adhesion to insulators, and increased costs due to the use of adhesion and barrier materials in damascene processing, complicating the bonding process.
Innovation Solution
Direct bonding methods, including uniform and hybrid bonding, are employed without adhesives, utilizing polished and activated non-conductive bonding layers that form strong chemical bonds at room temperature, and conductive features interdiffuse during annealing to create metal-to-metal connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper is used for conductive features, then conductivity is improved, but adhesion to insulators deteriorates
Solution Approach 1:
A barrier layer comprising chromium, molybdenum, tungsten, or their nitrides is introduced as an intermediary between the copper conductive features and the silicon oxide based dielectric material. This barrier layer serves dual functions: it prevents copper diffusion into the dielectric material and provides adequate adhesion between the copper and the dielectric, thereby resolving the adhesion problem while maintaining copper's superior conductivity.
2Strength
If adhesion and barrier materials are added to copper features, then adhesion and diffusion prevention are improved, but manufacturing complexity increases
Solution Approach 1:
The bonding layer is segmented into distinct functional components: a dielectric material layer and a conductive layer with copper features. The adhesion and barrier materials are selectively applied only to the conductive features where needed, rather than covering the entire bonding layer. This segmentation allows copper's superior conductivity to be utilized while minimizing the complexity introduced by additional materials.
3Reliability
If conventional bonding processes are used, then reliable bonds are achieved, but processing temperature and time increase
Solution Approach 1:
The bonding process parameters are optimized by reducing both temperature and time. The patent achieves reliable bonding at temperatures of 250°C or less and times of 30 minutes or less, compared to conventional processes that require higher temperatures and longer durations. This is accomplished through the use of a plasma treatment step that activates the bonding surfaces, enabling low-temperature bonding while maintaining bond reliability.
4Reliability
If copper features are used, then conductivity is improved, but dry etching difficulty increases
Solution Approach 1:
The patent extracts the copper features from the bonding layer formation process entirely. Instead of forming copper patterns through difficult dry etching, the conductive layer is deposited as a continuous film and subsequently patterned through electroplating into recesses. This extraction of copper from the etching process eliminates the dry etching difficulty while preserving copper's superior conductivity in the final bonded structure.
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 costs and complexity by eliminating the need for multi-step CMP processes and high-temperature annealing, enabling high-density connections with robust mechanical and electrical bonds.
Implementation Method 1
utilizing polished and activated non-conductive bonding layers that form strong chemical bonds at room temperature
Implementation Method 2
conductive features interdiffuse during annealing to create metal-to-metal connections
Implementation Method 3
conductive features interdiffuse during annealing
Data Source
AI summary
Disclosed herein are methods of forming a microelectronic component. In some embodiments, the method includes providing an element having a metallization layer that comprises a field dielectric and a conductive feature embedded in the field dielectric. The metallization layer also comprises a surface that includes the field dielectric and the conductive feature. The method further includes forming a copper feature over the conductive feature, forming a dielectric layer over sidewalls of the copper feature, and then planarizing the dielectric layer to form a hybrid bonding surface, where the copper feature is exposed at the hybrid bonding surface.