Pattern Registration Marks with Inner Outer Trenches for CMP Alignment
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Solution Overview
Problem
Existing pattern registration methods in semiconductor manufacturing, such as the box-in-box method, are inaccurate due to center-shifting issues during chemical-mechanical polishing, leading to misalignment of successive layers and defective devices.
Innovation Solution
The use of pattern registration marks with an inner and outer trench design, where the inner trench is completely filled by a conformal layer, providing a stationary reference point to compensate for center-shifting errors, and the outer trench is sized to remain partially filled, allowing for accurate alignment without damaging dry etching techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If chemical-mechanical polishing is used to remove conformal material outside the outer box, then material removal is achieved, but the center position of the outer box shifts leading to alignment errors
Solution Approach 1:
The patent introduces an inner box as an intermediary reference structure that is completely filled with conformal material. This inner box serves as a stable mediator that does not shift during CMP, allowing accurate alignment measurements to be taken relative to it, thereby resolving the center-shifting problem of the outer box while still enabling material removal.
Solution Approach 2:
The registration mark is segmented into two distinct components: an outer box for material removal and an inner box for reference. This segmentation allows the outer box to be processed by CMP for material removal while the inner box remains completely filled and stable, enabling separate optimization of each function without compromising the other.
2Loss of substance
If dry etching is used to remove conformal material outside the outer box, then selective material removal is achieved, but damage is caused to the etched surfaces and layer interfaces
Solution Approach 1:
The completely filled inner box acts as a protective intermediary structure. By taking alignment measurements relative to the inner box after CMP, the need for damaging dry etching is eliminated, as the inner box provides a stable reference that does not require additional protective measures against etch damage.
Solution Approach 2:
The patent converts the potential harm of CMP-induced center-shifting into a benefit by using the shifted outer box material as a detectable feature while relying on the stable inner box for accurate alignment. The harmful effect of CMP on the outer box center position is transformed into a useful topographical feature for detection, while the inner box provides the stable reference needed for precision.
3Ease of manufacture
If the outer box is partially filled with conformal material to create a detectable topography, then alignment detection is enabled, but the center position becomes difficult to measure accurately due to material re-positioning and residue
Solution Approach 1:
The registration mark is divided into two functional segments: the outer box that is partially filled to provide detectable topography for alignment detection, and the inner box that is completely filled to provide a stable, non-shifting reference center. This segmentation allows each component to fulfill its specific function without compromising the other.
Solution Approach 2:
The inner box serves as an intermediary reference structure that mediates between the detectable but unstable outer box and the alignment measurement process. By referencing the stable inner box rather than the shifting outer box center, accurate alignment measurements can be obtained despite the outer box's material re-positioning during CMP.
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 precise and accurate overlay alignment of successive patterns, reducing the risk of misalignment and device defects by using a conformal layer thickness and trench width relationships to maintain positional accuracy during planarization processes.
Implementation Method 1
a conformal layer disposed on the upper material layer and in the inner trench and the outer trench
Implementation Method 2
Chemical-mechanical polishing, while not causing interface damage like dry etching, suffers from the difficulty associated with the shift and/or rotation of the position of the material located in the outer trench
Data Source
AI summary
Pattern registration marks which include: a substrate and an upper material layer disposed above the substrate; an outer trench formed in the upper material layer, the outer trench having an outer trench width; an inner trench formed in the upper material layer, the inner trench having an inner trench width; and a conformal layer disposed in the inner trench and the outer trench, the conformal layer having a conformal layer thickness; wherein the outer trench width is greater than twice the conformal layer thickness, and wherein the inner trench width is less than or equal to twice the conformal layer thickness; and methods of using the same.