Conductive Pad Expansion Control for Low-Temperature Direct Bonding
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Solution Overview
Problem
Current methods for forming conductive pads in semiconductor elements lack effective control over metallic grain growth and expansion, leading to suboptimal bonding processes that require high thermal budgets and may result in defects such as nanovoids and inefficient metal-to-metal bonding.
Innovation Solution
The use of conductive pads with materials having different thermal expansion rates and unit cell sizes, combined with specific crystal orientations and surface treatments, allows for controlled expansion and direct bonding without adhesives, enabling lower temperature and shorter annealing times while minimizing thermal budget consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional bonding methods are used to form conductive pads, then bonding can be achieved, but high thermal budgets are required and defects such as nanovoids occur
Solution Approach 1:
The patent changes the material parameters of the conductive pad by using a multi-layer structure with different materials (e.g., copper layer with nickel barrier layer) having different coefficients of thermal expansion. This parameter change allows the conductive pad to control its own expansion behavior during annealing, achieving reliable bonding at lower thermal budgets while preventing nanovoid formation.
Solution Approach 2:
The patent employs composite material structure for the conductive pad, combining copper (or other metals) with barrier layers and optionally seed layers. This composite structure enables tailored thermal expansion characteristics, where the different materials compensate for each other's expansion/contraction behavior, allowing controlled expansion to ensure metal-to-metal contact without excessive thermal budget.
2Reliability
If conventional bonding methods are used to form conductive pads, then bonding can be achieved, but the process is inefficient and requires long annealing times
Solution Approach 1:
By changing the material composition and structure parameters of the conductive pad (multi-layer configuration with specific materials), the patent accelerates the bonding process. The controlled thermal expansion behavior enables faster formation of reliable metal-to-metal bonds, reducing annealing time from conventional lengthy processes to more efficient shorter durations.
3Ease of manufacture
If conductive pads are formed without controlled expansion, then simple processes can be used, but nanovoids and bonding defects occur
Solution Approach 1:
The patent uses composite material structure (copper layer with nickel barrier layer and optional seed layers) to inherently control thermal expansion behavior. This approach maintains manufacturing simplicity while ensuring bonding quality, as the multi-layer structure self-regulates expansion during annealing to prevent nanovoid formation without requiring complex additional process steps.
4Reliability
If high thermal budgets are used for bonding, then bonding can be achieved, but material costs increase and thermal damage risk increases
Solution Approach 1:
The patent changes the thermal expansion parameters through material selection and layer configuration, enabling bonding at lower temperatures. This reduces the thermal budget required, thereby lowering material costs (less thermal energy consumption) and reducing the risk of thermal damage to sensitive semiconductor structures, while still achieving reliable bonding.
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 facilitates reliable, high-density metal-to-metal bonding with reduced defects, lower material costs, and improved electrical contact at lower temperatures, enhancing the efficiency and reliability of semiconductor element stacking and bonding processes.
Implementation Method 1
The first conductive material has a unit cell size greater than a unit cell size of the second conductive material
Implementation Method 2
annealing the first conductive feature and the second conductive feature to bond the first conductive material of the first conductive feature and the second conductive material
Data Source
AI summary
An element and a bonded structure including the element are disclosed. The element can include a non-conductive region having a cavity extending at least partially through a thickness of the non-conductive region from the contact surface, and a contact feature formed in the cavity. The non-conductive region is configured to directly bond to a non-conductive region of a second element. The contact pad of the element is configured to directly bond to a contact pad of the second element. The contact pad can include a first conductive material and a second conductive material. The first conductive material can have a unit cell size greater than a unit cell size of the second conductive material. The first conductive material can be a metal alloying material. The first conductive material can be a metal silicide and the second conductive material can be a metal. A bonded conductive contact can include a conductive material and an alloying element, and an amount of the alloying element can vary through a thickness of the bonded conductive contact.