Trench-Based Support Structures for Semiconductor Membranes
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Solution Overview
Problem
Existing semiconductor device manufacturing methods are limited in achieving large-area thin semiconductor membranes due to horizontal support constraints, which restrict the extent of underetching and result in smaller SOI or SON structures, lacking mechanical stability and scalability.
Innovation Solution
A method involving the formation of a layered structure with a semiconductor layer on upper and lower etch stop layers, where first and second sets of trenches are created to provide a vertical support structure, allowing selective etching of the sacrificial layer, enabling a larger underetched area and increased mechanical stability by forming a wafer-scale semiconductor membrane attached to a bulk substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If horizontal support constraints are used to support the semiconductor membrane, then the membrane can be supported during processing, but the extent of underetching is restricted and large-area membranes cannot be achieved
Solution Approach 1:
The patent transitions from horizontal support (conventional method) to vertical support (invention). Trenches are formed extending vertically from the front surface through the membrane to the rear surface, with support structures filling these trenches to provide vertical support links between the membrane and substrate. This dimensional change enables large-area membranes to be underetched completely while maintaining mechanical stability through the vertical support architecture.
Solution Approach 2:
The patent segments the support function into discrete vertical support links formed by filling trenches with support structures. Instead of continuous horizontal support, the membrane is supported at multiple discrete vertical points through the thickness of the membrane. These segmented support links can be individually optimized and distributed across the membrane area to provide sufficient mechanical stability while enabling complete underetching.
2Area of moving object
If the membrane area is increased beyond horizontal support capabilities, then larger semiconductor devices can be manufactured, but the structure becomes mechanically unstable
Solution Approach 1:
The patent resolves the mechanical strength limitation by moving the support function to the vertical dimension. Trenches extend through the membrane thickness, and support structures filled into these trenches provide vertical load paths from the membrane to the substrate. This enables large-area membranes to maintain mechanical strength through vertical anchoring rather than horizontal bracing.
3Quantity of substance
If complete underetching is performed to achieve SOI or SON structures, then thin semiconductor membranes are obtained, but the process is limited to small areas due to support constraints
Solution Approach 1:
The patent enables complete underetching across large wafer areas by implementing vertical support through trenches that extend through the membrane. The support structures fill these vertical trenches, providing mechanical stability during complete sacrificial layer removal. This vertical support architecture removes the area limitation inherent in horizontal support methods, allowing full-wafer scale SOI or SON production.
Solution Approach 2:
The patent segments the underetching process into regions defined by the trench pattern. Each trench acts as an independent support element, allowing complete underetching to proceed in the spaces between trenches while maintaining overall structural integrity. This segmented approach enables complete sacrificial layer removal across large areas that would be unstable with continuous horizontal support.
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 the production of larger-area semiconductor membranes with enhanced mechanical stability, allowing for easier detachment and division into separate chips, reducing substrate costs, and facilitating re-use of the substrate, while also enabling standard etching techniques for membrane division.
Implementation Method 1
through the first set of trenches etching the sacrificial layer selectively to the upper etch stop layer and the lower etch stop layer
Data Source
AI summary
A method of manufacturing a semiconductor device wherein a laminate structure comprising a sacrificial layer is sandwiched between two etch stop layers (8,11) and which separates a semiconductor membrane (9) from a bulk substrate (1) is used to provide an underetched structure. Access trenches (4) and support trenches (5) are formed in the layered structure through the thickness of the semiconductor layer (9) and through the upper etch stop layer (8). The support trenches extend deeper through the sacrificial layer (12) and the lower etch stop layer and are filled. The sacrificial layer is exposed and etched away selectively to the etch stop layers to form a cavity (30) and realise a semiconductor membrane which is attached to the bulk substrate via a vertical support structure comprising the filled support trenches.