Rectangular Through-Wafer Vias High-Aspect Ratio Fabrication
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Solution Overview
Problem
Forming through-wafer vias with high-aspect ratios is challenging due to their difficulty in fabrication, as conventional methods struggle to effectively create vias with heights significantly greater than their widths.
Innovation Solution
A method involving the formation of a through-wafer via with a rectangular plate shape, where the height is at least ten times greater than the width, utilizing a trench with a length at least ten times greater than the width, filled with tungsten using CVD, and processed through lithographic and etching techniques, followed by dielectric layer formation and chemical mechanical polishing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional methods are used to form through-wafer vias, then the fabrication process is simpler, but the via quality and electrical connectivity deteriorate due to high-aspect ratio difficulties
Solution Approach 1:
The via formation process is divided into multiple sequential steps: forming a trench structure, depositing a first barrier layer, filling with conductive material, depositing a second barrier layer, and planarizing. This segmentation allows each step to be optimized independently, achieving high-aspect ratio via formation with improved precision while managing fabrication complexity through systematic process breakdown
Solution Approach 2:
Barrier layers are deposited on the sidewalls of the trench before filling with conductive material. This preliminary action prepares the trench structure in advance, ensuring proper adhesion and electrical isolation before the critical filling step, thereby improving via formation precision for high-aspect ratio structures
2Reliability
If the via height is increased to achieve through-wafer connectivity, then electrical connectivity improves, but the aspect ratio increases making fabrication more difficult
Solution Approach 1:
The invention changes the geometric parameters of the via structure by forming a rectangular plate shape with controlled length, width, and height ratios. The length is maintained at least ten times greater than the width, and the height is at least ten times greater than the width, optimizing both electrical connectivity and manufacturability through specific parameter relationships
Solution Approach 2:
The via structure comprises multiple materials including conductive fill material (such as tungsten or copper), barrier layers (such as tantalum nitride or tungsten nitride), and dielectric materials. This composite structure provides both excellent electrical connectivity and improved fabrication characteristics by combining materials with complementary properties
3Area of stationary object
If the via width is reduced to improve integration density, then device miniaturization improves, but the aspect ratio increases making via formation more difficult
Solution Approach 1:
The invention transitions from forming cylindrical via holes to forming rectangular plate-shaped vias with distinct length, width, and height dimensions. This dimensional change allows optimization of the cross-sectional area (length × width) independently from the height, enabling reduced via footprint while maintaining manageable aspect ratios through the rectangular geometry where length is at least ten times greater than width
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
Enables the successful formation of high-aspect ratio through-wafer vias with improved quality and electrical connectivity, facilitating efficient electrical paths through the semiconductor wafer.
Implementation Method 1
filled with tungsten using CVD
Implementation Method 2
processed through lithographic and etching techniques, followed by dielectric layer formation and chemical mechanical polishing
Data Source
AI summary
A through-wafer via structure and method for forming the same. The through-wafer via structure includes a wafer having an opening and a top wafer surface. The top wafer surface defines a first reference direction perpendicular to the top wafer surface. The through-wafer via structure further includes a through-wafer via in the opening. The through-wafer via has a shape of a rectangular plate. A height of the through-wafer via in the first reference direction essentially equals a thickness of the wafer in the first reference direction. A length of the through-wafer via in a second reference direction is at least ten times greater than a width of the through-wafer via in a third reference direction. The first, second, and third reference directions are perpendicular to each other.