Semiconductor Wafer Structural Supports for Deep Etch Warpage
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Solution Overview
Problem
Wafer warpage during semiconductor processing, particularly in deep etch processes for MEMS devices, leads to device failures, increased costs, and potential wafer breakage, which complicates tool maintenance and reduces yield.
Innovation Solution
Providing mechanical structural supports on the backside of semiconductor wafers during etching processes, using photomasks to define areas that will not be etched, thereby maintaining additional material and reducing warpage, which enhances the mechanical strength of the wafer and prevents breakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If deep etching is performed on the backside of the wafer to create MEMS cavities, then the MEMS device functionality is achieved, but the wafer structural integrity is reduced causing warpage and breakage
Solution Approach 1:
The patent applies local quality by selectively removing material only in specific cavity regions while preserving material in structural support regions. The etch process is spatially differentiated: deep cavities are etched in device areas while support areas maintain full thickness, creating local variations in material distribution that simultaneously enable MEMS functionality and maintain wafer strength.
Solution Approach 2:
The wafer backside is segmented into distinct functional zones: cavity regions where material is removed for MEMS device operation, and support regions where material is retained for structural integrity. This segmentation allows the wafer to fulfill dual roles - device functionality and mechanical support - by dividing the structure into specialized segments.
2Adaptability or versatility
If material is removed from the backside of the wafer to form deep cavities, then the MEMS device structure is created, but wafer warpage increases affecting processing quality
Solution Approach 1:
The patent implements local quality by creating spatially differentiated etching: deep cavities in device regions versus intact material in support regions. This local variation in material removal prevents uniform warping across the wafer while achieving the required MEMS cavity structures, thereby maintaining manufacturing precision in critical areas.
3Length of moving object
If the wafer is thinned to fit thinner packages, then the package thickness requirement is met, but the wafer becomes more susceptible to warpage and breakage
Solution Approach 1:
The patent applies local quality by maintaining different material thicknesses in different wafer regions. Support areas retain full or near-full thickness to provide mechanical strength, while device areas are thinned or etched to achieve package thickness requirements. This localized thickness variation satisfies both package constraints and strength requirements.
4Strength
If photomask areas are added to define structural support regions, then wafer warpage is reduced, but the photomask complexity increases
Solution Approach 1:
The photomask is segmented into distinct functional patterns: cavity definition areas and support area definition areas. This segmentation, while increasing mask design complexity, enables precise control over where material is removed versus retained, thereby achieving the dual goals of MEMS functionality and structural 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
The solution effectively reduces or eliminates wafer warpage, increasing device yield, lowering costs, and preventing tool damage by maintaining the structural integrity of the wafer during deep etch processes.
Implementation Method 1
providing areas on the photomask that correspond to the structural support areas, the structural support areas being areas that are not to be etched; using the photomask, performing an etch on the backside surface
Implementation Method 2
Some of these deep etches are performed on the backside of the wafer... One example of such an etch is a process known as Deep Reactive Ion Etching (DRIE) which is capable of performing very deep, high aspect ratio, anisotropic etches in silicon and polycrystalline silicon
Data Source
AI summary
Methods and apparatus for forming structures to reduce wafer warpage. A method includes providing a semiconductor wafer having a plurality of integrated circuits; providing a photomask defining a plurality of cavities to be formed by an etch on a backside surface of the semiconductor wafer; defining structural support areas for the backside surface, the structural support areas being contiguous areas; providing areas on the photomask that correspond to the structural support areas, the structural support areas being areas that are not to be etched; using the photomask, performing an etch on the backside surface of the semiconductor wafer to form the cavities by removing semiconductor material from the backside surface of the semiconductor wafer; and the structural supports on the backside of the semiconductor wafer formed as areas that are not subjected to the etch. Additional methods and apparatus are also disclosed.