Ion Beam Delayering for Uniform Large-Area IC Milling
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Solution Overview
Problem
Current delayering techniques for IC chips, such as mechanical polishing, chemical etching, plasma etching, and broad-beam ion milling, result in non-uniform material removal, micron-scale artifacts, and slow milling rates, making it difficult to achieve uniform planarity and precise control over the removal of multiple layers with varying thickness and composition.
Innovation Solution
A system utilizing a controlled ion beam with a cylindrical profile and adjustable ion density distribution, combined with a feedback control loop and detectors, to uniformly delayer IC chips across large areas, ensuring planarity and precise material removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If broad-beam ion milling is used to delayer IC chips, then material removal capability is improved, but uniformity of material removal deteriorates due to non-uniform ion density distribution
Solution Approach 1:
The patent applies local quality by varying the ion beam density distribution across different regions of the sample surface. The ion beam is designed with higher density at the edges and lower density at the center, compensating for the natural tendency of broad-beam ion milling to remove more material from the center. This non-uniform density distribution ensures uniform material removal across the entire sample area.
Solution Approach 2:
The patent changes the physical parameters of the ion beam, specifically the ion density distribution pattern. By adjusting the ion beam parameters to create a controlled non-uniform density profile, the system achieves uniform material removal despite using broad-beam ion milling. The ion beam parameters are optimized to balance material removal rate with uniformity across the sample surface.
2Area of stationary object
If mechanical polishing is used for delayering, then large area processing is improved, but surface quality deteriorates due to micron-scale artifacts and scratches
Solution Approach 1:
The patent replaces the mechanical polishing system with an ion beam-based system. Instead of using mechanical abrasives that create micron-scale scratches and artifacts, the invention uses ion bombardment to remove material through sputtering. This substitution eliminates mechanical contact and the associated surface damage while maintaining the ability to process large areas.
Solution Approach 2:
The patent changes the fundamental mechanism of material removal from mechanical abrasion to ion-induced sputtering. By controlling ion beam parameters such as energy, current density, and incidence angle, the system achieves smooth surface finish without the micron-scale artifacts characteristic of mechanical polishing.
3Productivity
If chemical etching is used for delayering, then material removal rate is improved, but uniformity deteriorates due to different etching rates of different materials
Solution Approach 1:
The patent replaces chemical etching with physical ion beam sputtering. Instead of relying on chemical reactions that have different rates for different materials, the system uses ion bombardment which removes material through physical ejection. This substitution eliminates the material-selectivity issue of chemical etching and achieves uniform removal across different materials in the IC chip stack.
4Manufacturing precision
If focused ion beam is used for delayering, then uniform material removal is improved, but productivity deteriorates due to slow milling rate and small milled area
Solution Approach 1:
The patent merges the advantages of focused ion beam (uniform removal) with the capabilities of broad-beam ion milling (high productivity). By using a broad ion beam with a specifically designed non-uniform density distribution, the system achieves both uniform material removal across large areas and high milling rates. The combination allows parallel processing of large sample areas while maintaining the uniformity typically associated with focused beams.
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
The system enables uniform delayering of IC chips with sub-millimeter to millimeter-scale areas and nanometer-scale depth resolution, allowing for precise analysis of chip structure and chemistry, and supports imaging and spectroscopic analysis.
Implementation Method 1
a controllable ion beam which maintains its profile over a long working distance... direct the ion beam at a glancing angle relative to the chip surface... segregate the ionic species within the beam and eliminate neutrally charged particles
Data Source
AI summary
A system and method for the precise and uniform material removal or delayering of a large area of a sample is provided. The size of the milled area is controllable, ranging from sub-millimeter to multi-millimeter scale and the depth resolution is controllable on the nanometer scale. A controlled singularly charged ion beam is scanned across the sample surface in such a manner to normalize the ion density distribution from the sample center toward the periphery to realize uniform delayering.