Surface Modified TSV Structure with Nickel Barrier
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Solution Overview
Problem
Current methods of revealing vias in microelectronic packages using copper can damage the silicon substrate due to thermal expansion and copper ion diffusion, leading to contamination and rendering the package unusable.
Innovation Solution
A method involving the deposition of a first metal, such as nickel or nickel alloy, within a substrate opening, followed by the deposition of a second metal, like copper or copper alloy, with a dielectric region to prevent damage and contamination, where the first metal acts as a barrier during substrate abrasion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper is deposited in the TSV and etching process is used to reveal the via, then electrical performance is optimized, but the silicon substrate is damaged due to thermal expansion and copper ion diffusion
Solution Approach 1:
A nickel barrier layer is introduced as an intermediary between the copper fill and the silicon substrate. This nickel layer serves as a diffusion barrier that prevents copper ions from migrating into the silicon during the etching process, while also providing thermal expansion compatibility. The nickel layer is deposited conformally on the silicon walls before copper fill, creating a protective interface that resolves the contradiction between achieving good electrical performance with copper and preventing substrate damage.
Solution Approach 2:
The TSV structure employs a composite material approach by combining multiple materials with complementary properties: nickel provides barrier and structural functions, copper provides electrical conductivity, and silicon dioxide provides dielectric insulation. This multi-material composite structure allows the system to simultaneously achieve optimized electrical performance, thermal stability, and protection against ion diffusion, resolving the technical contradiction.
2Reliability
If copper is deposited in the TSV, then electrical conductivity is improved, but copper ions diffuse and contaminate electrically active silicon regions
Solution Approach 1:
The nickel barrier layer acts as an intermediary that physically blocks copper ion diffusion into the silicon substrate. During the etching process, the nickel layer remains intact and prevents copper ions generated from the copper fill from migrating into the electrically active silicon regions. This intermediary layer maintains the high electrical conductivity of copper while eliminating the harmful diffusion effect.
3Ease of operation
If the etching process is used to reveal the via, then the TSV is exposed for connection, but the package is exposed to heat causing copper to expand more than silicon
Solution Approach 1:
The nickel barrier layer serves as a thermal expansion intermediary between copper and silicon. During the etching process, the nickel layer absorbs and accommodates the differential thermal expansion between copper and silicon, preventing mechanical stress and damage to the silicon substrate. This allows the via to be successfully exposed while mitigating the harmful thermal expansion effects.
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 the risk of substrate damage and contamination by copper ions, allowing for reliable electrical connections while maintaining the advantages of three-dimensional packaging with through-silicon vias.
Implementation Method 1
A dielectric layer may be deposited within the opening to cover the interior surface of the opening
Implementation Method 2
A first metal may be deposited within the opening so as to extend upwardly from a bottom of the opening towards the first face
Implementation Method 3
A second metal, which may be different from the first metal, may be deposited within the opening
Implementation Method 4
The substrate may be abraded from the second face to expose the first metal
Implementation Method 5
The bottom of the opening may be enlarged so that a first portion of the opening has a first width and a second portion of the opening has a second width
Data Source
AI summary
Microelectronic elements and methods of their manufacture are disclosed. A microelectronic element may include a substrate including an opening extending through a semiconductor region of the substrate, a dielectric layer cover a wall of the opening within at least a first portion of the opening, a first metal disposed within the first portion of the opening, a second metal disposed within a second portion of the opening. The second metal may form at least part of a contact of the microelectronic element.