Spin-on-glass ion implantation via barrier layer
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Solution Overview
Problem
Existing methods for forming spin-on-glass layers in integrated circuits face challenges such as moisture absorption and shrinkage issues during ion implantation, leading to 'poisoned via' problems and deplanarization, which are not adequately addressed by current ion implantation techniques that require high tilt angles and rotation of the wafer.
Innovation Solution
A method involving the formation of a spin-on-glass layer with a barrier layer, where the barrier layer is thinner or absent in the peripheral regions of holes or patterns, allowing for perpendicular ion implantation to concentrate the ions in these areas, thereby reducing moisture transfer and shrinkage risks without the need for high-angle implantation or wafer rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ion implantation is performed at high tilt angle with wafer rotation to treat exposed SOG sidewalls, then moisture release and poisoned via problems are addressed, but the manufacturing process becomes complex and deplanarization occurs
Solution Approach 1:
A barrier layer is deposited over the SOG layer before via formation, and this barrier layer is selectively removed or thinned in the via peripheral regions. This preliminary preparation enables subsequent perpendicular ion implantation to reach the SOG layer only where needed, avoiding the complexity of high-angle implantation with wafer rotation while still preventing moisture release and poisoned via problems
Solution Approach 2:
The barrier layer is designed with non-uniform thickness, being thinner or absent in peripheral regions around via holes and thicker in other regions. This local variation allows perpendicular ion implantation to selectively treat only the SOG layer in peripheral regions where moisture release occurs, maintaining via reliability while simplifying the manufacturing process and preserving SOG planarity in non-peripheral areas
2Device complexity
If perpendicular ion implantation is used to simplify the process, then manufacturing complexity is reduced, but ions cannot reach the exposed SOG layer in via sidewalls
Solution Approach 1:
The barrier layer serves as an intermediary structure that controls ion access to the SOG layer. By being thinner or absent in peripheral regions, it acts as a selective gateway that allows perpendicular ions to reach and treat the SOG layer only in areas where via sidewalls are exposed, preventing moisture release without requiring complex high-angle implantation geometries
3Reliability
If ion implantation is performed blanket over the SOG layer, then the entire SOG layer is cured, but shrinkage of almost 20% causes deplanarization
Solution Approach 1:
The barrier layer configuration creates localized ion implantation zones only in peripheral regions around via holes, rather than blanket implantation over the entire SOG layer. This selective treatment cures the SOG layer where moisture release occurs (peripheral regions) while leaving the central regions untreated, thereby preventing the 20% shrinkage-induced deplanarization that would result from full-area implantation
4Ease of manufacture
If the barrier layer is made thinner in peripheral regions to allow ion penetration, then targeted implantation is achieved, but the barrier layer protection is reduced in those areas
Solution Approach 1:
The barrier layer is designed with spatially varying thickness: thin or absent in peripheral regions to enable ion penetration and SOG curing where moisture release occurs, and thick in other regions to provide adequate protection. This local differentiation allows the barrier layer to simultaneously provide protection where needed and accessibility where required, without compromising overall device reliability
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 enables deeper and more targeted ion implantation, reducing the risk of deplanarization and moisture-related issues, simplifies the manufacturing process, and allows for the use of narrower or non-rotationally symmetrical holes, while maintaining the planarizing properties of the spin-on-glass layer.
Implementation Method 1
Ion implantation of the SOG has been reported as a solution for the poisoned via problem. The ion implantation further cures the SOG material and so prevents the absorption and release of moisture.
Data Source
AI summary
A spin on glass SOG layer 30 is formed, then a PECVD barrier layer 40 over the SOG layer. Holes 50 in the SOG layer for vias are formed with a wine glass profile, so that in a peripheral region around the periphery of the holes, the barrier layer is thinner or absent, and ion implantation is performed substantially perpendicular to the layers, to reach the SOG layer through the barrier layer preferentially in the peripheral region. This enables the implantation to be concentrated on the peripheral region, without the need for implantation at a high angle and wafer rotation. This enables the manufacturing process to be simplified and hence costs reduced. By concentrating the implantation in the peripheral region where it can reduce moisture transfer to material in the holes, there is less risk of deplanarization due to the SOG shrinkage associated with ion implantation.