Staged TSV Structure for Backside Reveal and Hybrid Bonding
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Solution Overview
Problem
Existing methods for forming through-substrate vias (TSVs) face challenges such as variations in via depth, which can lead to issues like smearing of conductive material, substrate contamination, and breakage of TSVs during backside reveal and subsequent processing.
Innovation Solution
The formation of TSVs involves creating a staged TSV structure with multiple materials, where deep vias are partially filled with a first material from the front side and the remainder filled with a second material. The first material is revealed during backside thinning, allowing for hybrid bonding preparation. This approach can include using a sacrificial tip material that is replaced to form a conductive tip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If via structures are filled with conductive material from the front side, then electrical connectivity is established, but depth variations cause smearing and contamination during backside reveal
Solution Approach 1:
The via fill process is segmented into two distinct stages: first filling deep portions with a sacrificial material, then filling remaining portions with conductive material. This segmentation allows the sacrificial material to protect against smearing during backside reveal while still enabling electrical connectivity, thus resolving the contradiction between reliability and contamination prevention.
Solution Approach 2:
A sacrificial material is introduced as an intermediary substance that temporarily occupies the deep portions of via structures. This intermediary material prevents smearing and contamination during backside substrate reveal, and is subsequently removed to allow proper conductive material filling, thereby eliminating the harmful effects while maintaining reliability.
2Reliability
If deep vias are fully filled from the front side, then electrical connectivity is achieved, but variations in via depth lead to breakage during processing
Solution Approach 1:
The via filling operation is divided into two sequential steps: first filling deep regions with sacrificial material to provide structural support, then filling the remaining shallower portions with conductive material. This segmentation prevents breakage by ensuring deep portions are supported during processing while still achieving electrical connectivity.
Solution Approach 2:
The sacrificial material serves as a cushioning element placed beforehand in deep via portions to prevent structural failure during backside reveal and subsequent processing. This prior cushioning protects the via structures from breakage, and the material is later removed to complete the conductive filling.
3Productivity
If backside reveal is performed on substrates with varied via depths, then TSV formation is completed, but smearing of conductive material occurs
Solution Approach 1:
The sacrificial material acts as a protective intermediary during backside reveal, preventing smearing of conductive material even when via depths vary. This allows the backside reveal process to proceed efficiently without compromising the precision of via filling, as the sacrificial material is removed after reveal to expose clean via openings.
Data Source
AI summary
Disclosed is a microelectronic structure including a first element and a through substrate via (TSV) structure. The first element includes a bulk portion having a front side and a back side opposite the front side. The TSV structure is disposed in an opening extending at least partially through the bulk portion from the front side to the back side. The TSV structure includes a conductive tip portion and a second conductive via portion. The second conductive via portion is disposed between the front side and the conductive tip portion. The conductive tip portion contains a different conductive material than the second conductive via portion.